Physics Letters B 784 (2018) 101–111Contents lists available at ScienceDirectPhysics Letters Bwww.elsevier.com/locate/physletbObservation of the decay Λ0b→ Λ+cppπ−

University of Groningen

Physics Letters B 784 (2018) 101–111Contents lists available at ScienceDirectPhysics

Letters Bwww.elsevier.com/locate/physletbObservation of the decay Λ0b→ Λ+cppπ−

Onderwater, C. J. G.; LHCb Collaboration

Published in:

Journal of High Energy Physics

DOI:

10.1016/j.physletb.2018.07.033

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Onderwater, C. J. G., & LHCb Collaboration (2018). Physics Letters B 784 (2018) 101–111Contents lists

available at ScienceDirectPhysics Letters Bwww.elsevier.com/locate/physletbObservation of the decay

Λ0b→ Λ+cppπ−. Journal of High Energy Physics, 784, 101-111.

https://doi.org/10.1016/j.physletb.2018.07.033

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Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Observation

of

the

decay

Λ

_b

0

→ Λ

+

_c

p p

π

−

.

LHCb

Collaboration

a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory:

Received27April2018

Receivedinrevisedform29June2018 Accepted17July2018

Availableonline25July2018 Editor: W.-D.Schlatter

ThedecayΛ0_b→ Λ+cp p

π

−isobservedusingpp collisiondatacollectedwiththeLHCbdetectorat centre-of-massenergiesof√s=7 and8 Tev,correspondingtoanintegratedluminosityof3 fb−1.Theratioof branchingfractionsbetweenΛ_b0→ Λ+cp p

π

−andΛ0b→ Λ+c

π

−decaysismeasuredtobe

B(Λ0_b→ Λ+_cp p

π

−) B(Λ0_b→ Λ+c

π

−)

=0.0540±0.0023±0.0032.

Two resonant structures are observed in the Λ+c

π

− mass spectrum of the Λ0b→ Λ+cp p

π

− decays, corresponding tothe Σc(2455)0 and Σc∗(2520)0states. Theratios ofbranchingfractionswith respect tothedecayΛ_b0→ Λc+p p

π

−are

B(Λ0_b→ Σ_c0p p)×B(Σ_c0→ Λ+_c

π

−) B(Λ0 b→ Λ+cp p

π

−) =0.089±0.015±0.006, B(Λ0_b→ Σ∗0 c p p)×B(Σc∗0→ Λ+c

π

−) B(Λ0_b→ Λ+c p p

π

−) =0.119±0.020±0.014.

Inalloftheaboveresults,thefirstuncertaintyisstatisticalandthesecondissystematic.Thephasespace isalsoexaminedforthepresenceofdibaryonresonances.Noevidenceforsuchresonancesisfound.

©2018TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

The quark model of Gell-Mann [1] and Zweig [2] classifies mesons (qq) and baryons (qqq) into multiplets, and also allows forhadronswithmorethantheminimalquark contents.In2015, LHCbobservedtwopentaquarkstatesinthedecay

Λ

0_b

→

J

/ψ

p K−

[3].Inthedecaychannel

Λ

0_b

→ Λ

+_c p p

π

−,1charmeddibaryon res-onantstatescouldbepresent.AsdiscussedinRef. [4],suchstates could manifest via the decay

Λ

0_b

→

p

+ [

cd

][

ud

][

ud

] =

p

+

D

_c+, where

D

_c+ isthedibaryon statewithamassbelow4682 MeV

/

c2_. Thesubsequentdecayofthe

D

_c+dibaryoncouldproceedeithervia quark rearrangement to the final state p

Σ

_c0, with

Σ

_c0

→ Λ

+_c

π

−, or via string breaking to the final state

P

_c0

(

u

¯

[

cd

][

ud

])

, which could involve a lighter, yet undiscovered

P

_c0 pentaquark state,

D

+

c

→

P

c0

(

u

¯

[

cd

][

ud

])

p, with

P

c0

→ Λ

+c

π

− [4]. The discovery of

anyofthesedecaymodeswouldtestthe predictionsofquantum chromodynamics and the fundamental workings of the Standard Model.

1 _{Unlessexplicitlynoted,chargeconjugatedecaysareimplied.}

InthisLetter,thefirstobservationofthedecay

Λ

_b0

→ Λ

+c p p

π

−,

referred to as the signal channel, is reported. A measurement is made of its branching fraction relative to the normalisation channel

Λ

0_b

→ Λ

+_c

π

−.Resonance structureswithin the

Λ

+_c p p

π

− systemarealsoinvestigated.Whilenoevidencefordibaryon reso-nancesisfound,significantcontributionsfromthe

Σ

c

(

2455

)

0 and

Σ

c∗

(

2520

)

0 resonances are found in the

Λ

+c

π

− invariant mass

spectrum. The ratios of branching fractions between decays via these resonances, hereinafter denoted as

Σ

_c0 and

Σ

_c∗0, and the

Λ

+_cp p

π

−inclusivedecayarealsoreported.Themeasurements in this Letterare basedon a data sample of pp collisions collected withtheLHCb detectoratcentre-of-massenergies of

√

s

=

7 Tev in 2011and

√

s

=

8 Tev in2012, corresponding to an integrated luminosityof3 fb−1.

2. Detectorandsimulation

The LHCb detector [5,6] is a single-arm forward spectrome-tercoveringthe pseudorapidity range2

<

η

<

5,designedforthe studyofparticles containingb or c quarks.The detectorincludes a high-precision trackingsystem consistingof a silicon-strip

ver-https://doi.org/10.1016/j.physletb.2018.07.033

0370-2693/©2018TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3_.

tex detector surrounding the pp interaction region, a large-area silicon-strip detector located upstream of a dipole magnet with a bending power of about 4 Tm, and three stations of silicon-strip detectors and straw drift tubes placed downstream of the magnet. Different typesofcharged hadronsare distinguished us-ing information from two ring-imaging Cherenkov (RICH) detec-tors.Photons,electrons andhadronsareidentifiedby a calorime-ter system consisting of scintillating-pad and preshower detec-tors, an electromagnetic calorimeter and a hadronic calorimeter. Muons are identified by a system composed of alternating lay-ersofironandmultiwireproportionalchambers.Theonlineevent selection isperformedby atrigger [7], whichconsistsofa hard-warestage,basedoninformationfromthecalorimeterandmuon systems,followedbyasoftwarestage,inwhichallcharged parti-cleswith pT

>

500

(

300

)

MeV

/

c arereconstructedfor2011(2012) data,where pT isthetransversemomentum [7]. Atthehardware trigger stage, events are required to contain a muon or dimuon pair with high pT, or a hadron, photon or electron with high transverseenergydepositedinthecalorimeters.Thesoftware trig-ger requires a two-, three- or four-track secondary vertex with a significant displacement from any primary proton–proton in-teraction vertices (PVs). At least one chargedparticle must have a pT

>

1

.

7

(

1

.

6

)

GeV

/

c for2011 (2012) data,and be inconsistent withoriginating from a PV. A multivariate algorithm [8] is used fortheidentificationofsecondaryverticesconsistentwiththe

de-cayofab hadron.

Simulated samples of the signal, the normalisation channels and backgrounds produced in pp collisions are generated using Pythia [9] with a specific LHCb configuration [10]. Decays of hadronic particles are described by EvtGen _{[11], in which} final-state radiationis generatedusingPhotos_{[12].The interaction of} thegeneratedparticleswiththedetector,anditsresponse,are im-plementedusingtheGeant4toolkit [13] asdescribedinRef. [14].

3. Candidateselection

The

Λ

0_b

→ Λ

+_c p p

π

− and

Λ

0_b

→ Λ

+_c

π

− candidates are recon-structed using the decay

Λ

+_c

→

p K−

π

+. An offline selection is applied, based on a loose preselection, followed by a multivari-ateanalysis. Tominimize the systematicuncertaintyon the ratio ofefficienciesbetweenthesignalandthenormalisationchannels, the selection criteriaon the

Λ

_c+ candidates are similar between thetwochannels.

Reconstructed final-state particles in

Λ

_b0

→ Λ

+c p p

π

− and

Λ

0_b

→ Λ

+c

π

− candidate decays are required to have a

momen-tump

>

1 GeV

/

c and pT

>

100 MeV

/

c.Protonsandantiprotonsare required to have p

>

10 GeV

/

c to improve particle identification. All final-state particles are also required to be inconsistent with originatingfromanyPV, by rejectingthetracks witha small

χ

2

IP, where

χ

2

IP is the difference in the vertex-fit

χ

2 _{of a given PV} withorwithoutthetrackconsidered,requiring

χ

2

IP

>

4.Candidate

Λ

+c decaysare required tohave atleast one decayproduct with pT

>

500 MeV

/

c and p

>

5 GeV

/

c,a goodvertex-fitquality,andan invariant mass within

±

15 MeV

/

c2 of the known

Λ

+_c mass [15]. Thescalarsumofthetransversemomentaofthe

Λ

+c decay

prod-uctsisrequiredtobegreaterthan1.8 GeV

/

c.

The

Λ

+_c

π

−candidateisreconstructedbycombininga

Λ

+_c can-didatewith a pion, andthe signal candidate is reconstructed by combininga

Λ

+c candidatewitha pion,aprotonandan

antipro-ton.These combinationsmustforma

Λ

0_b candidatewitha good-qualityvertexandbe consistentwithoriginatingfromthe associ-atedPV,definedasthatforwhichthe

Λ

0_b candidatehastheleast

χ

2

IP. Furthermore, the

Λ

+c candidate is required to decay

down-streamofthe

Λ

0_b decayvertex. The

Λ

0_b decaytime,calculated as

t

=

m_Λ0

bL

/

p, is required to be greater than 0.2 ps, where mΛ 0 b is

the mass, L is the decaylength and p is the momentum of the

Λ

0_b candidate.The

Λ

0_b candidateis alsorequired to haveatleast one final-state particle in the decay chain with pT

>

1

.

7 GeV

/

c,

p

>

10 GeV

/

c,andhaveatleastonetracksignificantlyinconsistent withoriginatingfromtheassociated PVbyrequiring thetrackto have

χ

2

IP

>

16.Final-statetracksofsignal andnormalisation chan-nelcandidatesmustpassstrictparticle-identificationrequirements based on the RICH detectors, calorimeters and muon stations. A constrainedfit [16] isappliedtothecandidatedecaychainforboth the signal andthenormalisation channels, requiringthe

Λ

0_b can-didate to comefrom the associatedPV andconstraining the

Λ

+c

particle to its knownmass [15]. Inthe caseof thesearch of the resonant contributions,themassofthe

Λ

0_b candidateisalso con-strainedtotheknownmass [15].

Triggersignalsareassociatedwithreconstructedparticlesfrom the decays of the signal channel or of the normalisation chan-nel. Selection requirementscan thereforebe madeonthe trigger selection itself and on whether the decision was dueto the re-constructed candidate decay, other particles produced in the pp

collision, or a combination ofthe two. This association makes it possible to usea data-driven methodforthe correction and sys-tematic uncertainty estimation on the trigger efficiencies [7]. To take advantage ofthe similaritybetweenthe signal andthe nor-malisation channels, whichhelpsto minimize thesystematic un-certaintyontheratiooftheirefficiencies,candidatesareclassified inoneofthefollowingtwohardwaretriggercategories.Inthefirst category, calledTriggeredOnSignal(TOS), thecandidatemust in-cludeahadronconsistentwithoriginatingfromthedecayofa

Λ

+_c

candidate and which deposited enough transverse energy in the calorimetertosatisfythehardwaretriggerrequirements.The typ-icalvalueofthetransverseenergythresholdisaround3.5 GeV

/

c2_. As the

Λ

+_c baryon is a

Λ

0_b decay product for both the signal andthe normalisationchannels, thischoice minimizesthe differ-ence between the

Λ

0_b decay modes. The second category, called TriggeredIndependentofSignal(TIS),compriseseventswhich sat-isfied the hardware trigger through signatures unassociated with the complete

Λ

0_b decay chains, either dueto a muon withhigh

pT,ora hadron, photon,or electronwithhigh transverseenergy deposited inthecalorimeters.The efficienciesofthe TISandTOS requirementsaredifferent,sothedataaredividedintotwo statis-tically independentsamples, one TIS, andthe other TOS andnot TIS,whichwillbereferredtoasTOSfortherestofthisLetter.

The so-called cross-feed backgrounds, contributing under the peak of the invariant mass of the normalisation channel or of the signal channel from the B0

(

B_s0

)

→

D+

(

D+_s

)

π

− and B0

₍

_B0

s

)

→

D+

(

D+s

)

p p

π

− decays, respectively, with D+

(

D+_s

)

→

K+K−

π

+ or D+

→

K−

π

+

π

+,whereeitherthekaon or pion is misidentified as a proton, are explicitly vetoed when both ofthefollowingtwo conditionsaresatisfied.First,the mass hypothesis oftheprotonfromthe

Λ

+c candidateisreplacedwith

either the kaon or pion hypothesis, and the resulting invariant mass of the combination is consistent with the known D+

(

D+_s

)

mass [15] within

±

15 MeV

/

c2. Second, theinvariant massof the

Λ

+c candidateissettotheknown D+

(

D+s

)

mass [15],andthe

re-sulting invariantmassof the

Λ

_b0 candidateisconsistent withthe known B0

₍

_B0

s

)

mass [15] within

±

25 MeV

/

c2 for

Λ

0b

→ Λ

+c p p

π

−

decays,andwithin

±

45 MeV

/

c2 _for

_Λ

0

b

→ Λ

+c

π

− decays.

Further backgroundreduction isachievedusing amultivariate analysis based on a gradient boosted decision tree (BDTG) [17]. The BDTG is trained using twelve variables: the vertex-fit qual-ity ofthe

Λ

c+ and

Λ

0b candidates,the decay-vertex displacement

along thebeamline betweenthe

Λ

0_b and

Λ

+c candidates, the

the associated PV, the

χ

2

IP of the

Λ

0

b candidate, the angle

be-tweenthereconstructed

Λ

0_b momentumandthedirectionofflight fromthe associatedPV to the decayvertex, the smallest pT and smallest

χ

2

IP among the three

Λ

+c decay products, the pT and

χ

2

IP of the pion originating directly from the

Λ

0b decay, and the

smallest pT and smallest

χ

IP2 between the p and p originating directlyfrom the

Λ

0_b decay. The BDTG training is performed us-ing simulated samples for the signal, and data distributions for thebackground,withreconstructedinvariantmasswellabovethe known

Λ

_b0 mass [15]. Cross-feed backgrounds from the decays

Λ

0_b

→ Λ

+cK+K−

π

−, B0

→ Λ

c+p

π

+

π

− and Bs0

→ Λ

+cp K+

π

− are

explicitly vetoed during the BDTG-training process by requiring the difference between the reconstructed b-hadron mass and its knownmass tobe greater than

±

30 MeV

/

c2. The BDTGselection isoptimizedforthefigureofmerit S

/

√

S

+

B,where S andB are

theexpectedsignal andbackgroundyields within

±

30 MeV

/

c2 _of the known

Λ

0_b mass [15]. The initial value of S and B without

BDTGselectionisobtainedfromthe

Λ

0_bmassspectrumindata.No improvementinthenormalisationchannel isfoundusinga simi-larprocedure,thereforenoBDTGselectionisapplied.Asystematic uncertaintyisassessedforthischoiceinSection6.

Duetothe largenumberoffinal-stateparticles inthe

Λ

0_b de-cays, particles with the same charge may share track segments, representing a possible background. These tracks are referred to asclones,andaresuppressedbyrequiringthattheopeningangle betweenanysame-charged tracksin thecandidate islarger than 0.5 mrad. This selection removes 2% of candidates in the signal sampleand0.1%inthenormalisationsample. Ifmultiple

Λ

0_b can-didatesarereconstructedinonesingleevent,onecandidateis cho-senatrandominthefollowingtwocases.First,iftheprotonfrom the

Λ

+c decaysisexchangedwiththatdirectlyfromthe

Λ

0b decays,

formingtwocandidateswithnearlythesame

Λ

0_b mass.Second,if a track fromone candidate shares a segment witha trackfrom another candidate.With these criteria, 2.5% of candidates in the signalsampleand0.1%inthenormalisationsamplearevetoed. Af-tertheseselections, 0.8%ofeventsin thesignalsample and0.2% inthenormalisationsamplecontainmultiple

Λ

0_bcandidates.These remaining multiplecandidates mainlyoriginate fromthe random combinationsofthefinal-statetracks,andhaveanegligible influ-enceontheestimation ofthesignal yields. No furthervetoes on thesecandidatesareapplied.

4. Efficiencies

Thetotalefficienciesofthesignalandthenormalisationdecays aregivenby



total

=



a

·



rec&sel|a

·



trig|sel

·



PID

,

(1) where



a represents thegeometrical acceptance ofthe LHCb de-tector,



rec&sel|a is the efficiency of reconstruction and selection calculated on candidates in the acceptance,



trig|sel is the trig-gerefficiencyoftheselected candidates,and



PID isthe particle-identificationefficiency.Allefficienciesexcept



PID and



trig|selare determined from simulation.The particle-identification efficiency is determined from calibration data specific to each data-taking year, binned in momentum and pseudorapidity of the track in question, as well as in the multiplicity of the event [18]. The trigger efficiency is determined from a combination of simula-tion and data-driven techniques where the agreement between dataand simulationis explicitly verified usingthe normalisation sample satisfying the TIS requirement. All efficiencies are calcu-lated separately for the TIS and TOS trigger samples, and for data-takingyear,duetothedifferenceincentre-of-massenergies.

Agreementbetweendataandsimulationisimprovedby applying aper-candidateweighttothepT andrapidity, y,ofthe

Λ

0_bbaryon insimulatedeventstomatchthenormalisationsampleintheTIS category, which is largely independent of trigger conditions.The

pTand y distributionsof

Λ

0_bproducedinpp collisionareidentical for the signal andthe normalisation channels, so the same per-candidateweightsareappliedtothesignalsample.Thesimulated

χ

2

IP ofthe final-stateparticles andthevertex-fit

χ

2 _of

_Λ

+

c

candi-dates are weighted to reproducethe datadistributions. The ratio betweentheefficienciesofthesignalandthenormalisation chan-nels,



r,is

(

10

.

00

±

0

.

12

)

% fortheTISsampleand

(

11

.

39

±

0

.

22

)

%

fortheTOSsample,includinguncertaintiesduetothelimitedsize ofthesimulatedsample.

5. Fitmodelandtheratioofbranchingfractions

The yields in both the signal and the normalisation channels are determined froman unbinned extended maximum-likelihood fitto thecorresponding invariant-mass spectrawithboththe TIS andTOS samples combined.The signal is modelled by a sum of twoCrystalBallfunctions[19] withacommonmeanofthe Gaus-siancore, andwiththetailparametersfixed fromsimulation.For both the signal and the normalisation channels, the background fromrandomcombinationsof final-stateparticlesisdescribed by an exponential function, whose parameters are left free in the fits and are independent betweenthe signal and the normalisa-tionchannels.Forthenormalisationchannel,backgroundfromthe

Λ

_b0

→ Λ

+c

ρ

−decays,with

ρ

−

→

π

−

π

0ismodelledbythe

convo-lutionofan empirical thresholdfunctionwitha Gaussian resolu-tion.Thecontributionduetomisidentificationofthekaontopion from

Λ

0_b

→ Λ

+cK− ismodelledbyasumoftwoCrystalBall

func-tions. Theparameters ofthesetwobackground sourcesare taken from simulation. The fits to the invariant-mass distributions for thesignal andthenormalisationchannelsareshowninFig. 1.In thisfigure,theTISandTOSsamplesarecombined.Fromthesefits, 926

±

43

Λ

0_b

→ Λ

+_cp p

π

−and

(

167

.

00

±

0

.

50

)

×

103

_Λ

0

b

→ Λ

+c

π

−

decaysareobserved.

To determine the ratio of branching fractions B(Λ

0

b→Λ+cp pπ−) B(Λ0

b→Λ+cπ−)

, indicated inthe followingby

B

r,a simultaneousfit isperformed

to the signal and the normalisation channels, each divided into the two independent trigger categories. The yield of the nor-malisation sample, N

(Λ

0_b

→ Λ

c+

π

−

)

, is a free parameter in the

fits, whereas the yield of the signal sample is calculated as

N

(Λ

0_b

→ Λ

+_c p p

π

−

)

=

B

r

×



r

×

N

(Λ

0_b

→ Λ

c+

π

−

)

, where



r is the

ratio between the total efficiency of the

Λ

0_b

→ Λ

+_cp p

π

− and

Λ

_b0

→ Λ

+_c

π

− decays. The ratio of branching fractions

B

r is the

same for the TIS and TOS subsamples and is measured to be

B

r

=

0

.

0542

±

0

.

0023.The corresponding signal yields are 677

±

29 forthe TISsubsample and259

±

11 forthe TOS subsample; theyieldsinthenormalisationsampleare

(

124

.

9

±

0

.

4

)

×

103 for theTISsubsampleand

(

41

.

9

±

0

.

2

)

×

103 fortheTOSsubsample.

6. Systematicuncertainties

The systematicuncertainties on themeasurement ofthe ratio of branching fractions are listed in Table 1. The total systematic uncertaintyisdeterminedfromthesuminquadratureofallterms. First, the uncertainty related to the background modelling is considered. In the signal sample, the exponential function is re-placedwithasecond-orderpolynomialforthebackground compo-nent.Forthenormalisationchannel,themodelisvariedby using thesumoftwoexponentialfunctions.Theresultinguncertaintyon the ratio ofbranching fractions is 0.6%. The uncertainties dueto the

Λ

0_b

→ Λ

+c K−shapeparametersareassessedbyincreasing the

Fig. 1. Invariantmassdistributionsofthe(a)Λ0

b→ Λ+cp pπ− and(b)Λ0b→ Λ+cπ− candidates.Fitresultsareoverlaidasasolidblueline.For(a),thereddottedline

representsthesignalcomponentandthegreendottedlinethebackgroundduetorandomcombinations.For(b),thereddottedlineisthesignalcomponent,thegreendotted lineistherandomcombinationbackground,thepurpledashedlineisthecontributionfromΛ0b→ Λ+cρ− andthebrowndashed–dottedlinerepresentsthecontribution

fromΛ0

b→ Λ+cK−.(Forinterpretationofthecoloursinthefigure(s),thereaderisreferredtothewebversionofthisarticle.)

Table 1

Summaryofsystematicuncertaintiesandcorrectionfactorstotheratioofbranchingfractions measurement.Alluncertaintiesaregivenasapercentageoftheratioofbranchingfractions.

Source Uncertainty (%) Correction factor

Background fit model 0.7 –

Signal fit model 0.1 –

PID efficiency 0.3 –

Tracking efficiency calibration 0.8 0.985 Kinematic range of final-state tracks 0.7 –

Hadron interaction 4.4 –

pT,y weighting 1.0 –

Trigger efficiency 2.9 –

Simulated sample size 1.3 –

Candidates with clone tracks and multiple candidates 0.2 – Veto of the reflection background 0.4 –

Λ+c Dalitz weighting 0.2 0.984

Λ+c polarization 0.3 0.987

Resonant structures 1.8 1.041

Total 6.0 0.996

widthofthe Crystal Ballfunctionsby 10%,corresponding to two standarddeviations,resultinginachangeof0.1%.Theuncertainty duetothe

Λ

0_b

→ Λ

_c+

ρ

− contributionisestimatedby varyingthe shapeparametersbyonestandarddeviation,resultinginan uncer-taintyof0.4%.Thetotaluncertaintyonthe ratioofthebranching fractionsduetothebackgroundmodellingis0.7%.

Thesignal-modelparameterizationischangedtoasingle Hypa-tiafunction [20],wherethemean andwidthare allowedto float andallotherparametersaretakenfromsimulation,resultinginan uncertaintyof0.1%.

Theuncertainty onthe relativeefficiencyof theparticle iden-tification is assessed by generating pseudoexperiments. For each pseudoexperiment, efficiencies in different momentum, pseudo-rapidity and multiplicity bins are determined from independent Gaussiandistributions withmeanvaluesequaltothenominal ef-ficiencies and widths corresponding to their uncertainties. This procedure is repeated 1000 times, and the width of the result-ing efficiency is taken asthe systematic uncertainty. This proce-dure, performed separately for the TIS and TOS samples, results in a 0.13% uncertainty for both samples. Binning effects on the efficiency are estimated by halving the bin size of the momen-tumdistributions,resultinginarelativechangeof0.2%fortheTIS sampleand0.1%fortheTOSsample.The totaluncertaintyonthe relativeefficiencyfortheTISandTOSsamplesis0.24%and0.16%, respectively,corresponding toan uncertaintyof0.3% onthe ratio ofthebranchingfractions.

Tracking efficiencies are determined with simulated events weighted tomatchthe kinematicpropertiesofdedicated

calibra-tion samples. The weights are determined as a function of the kinematicvariables,separately foreachdata-taking year [21].The kinematic properties of the

Λ

_c+ decay products are similar for the signal and the normalisation samples and therefore provide minorcontributionstothetotaltrackingefficiencyratio.The dom-inant contribution to the systematicuncertainty comes from the knowledge ofthe p and p tracking efficiencies,whosesystematic uncertainties are fullycorrelated. Theefficiencycorrection proce-dure gives a change inefficiency of2.0% for theTIS sample and 1.4%fortheTOSsample,yieldingatotalcorrectionfactorof0.985 for theratio ofbranching fractions, anda systematicuncertainty

of0.4% foreach ofthe p and p mainlystemming fromthefinite

sizeofthecalibrationsample [21].

Due todistinct triggerrequirements,thekinematicacceptance ofthe calibrationsamplesdiffersslightlyfromthesignal andthe normalisationchannels.Anonnegligiblefractionofcandidateshave final-state particles in a kinematic range outside of the regions covered by the calibrationsamples. About 20% of the candidates frombothchannelsfallinthiscategoryduetothelow-momentum pionfromthe

Λ

+_c decay. Inaddition,10% ofthecandidatesfrom the signalchannel arealsoaffected,mainly dueto thepion orig-inating from the

Λ

0_b decay.For all of these outside-range candi-dates,theefficiencycorrectioninthenearestavailablebinisused. Astheeffectsfor

Λ

+c decayscancelintherelativeefficiency,only

the additional 10% candidates in the signal channel contribute a 0.7%uncertaintyontherelativeefficiency.

HadronicinteractionswiththeLHCb detectorcontributean ad-ditionaluncertaintyof2.2%ontheratioofthebranchingfractions

foreach p orp (4.4%intotal),whichisobtainedfromsimulation, accountingfortheimperfectknowledgeofmaterialbudgetofthe LHCb detector[22].

Per-candidate weights depending on pT and y of the

Λ

0_b baryon are applied in simulated events to improve the agree-ments betweendata andsimulation. Systematicuncertainties for theweighting dueto the finitesize of the normalisation sample areassessed withpseudoexperiments.Ineach pseudoexperiment, theweights are varied within their uncertainties, andtheresults are propagated to the ratio of branching fractions. The standard deviation of the obtained distributions is taken as a systematic uncertainty, resulting in 0.65% for the TIS sample and 0.65% for theTOS sample. Thesystematic uncertainties dueto the binning scheme of the weighting in pT and y are estimated by halving thebinsize,orusingthegradientboosting [23] [24],whichisan unbinnedmethodof weighting, tocheck the changeson the rel-ativeefficiencies.The resultingsystematicuncertaintiesare 0.43% fortheTISsampleand1.5%fortheTOSsample.Afterpropagation throughthe entirefitprocedure, thisresultsinan uncertaintyof 1.0%ontheratioofthebranchingfractions.

TriggerefficienciesfortheTOSsamplesarealsoassessedusing pseudoexperiments which are propagated to the final measure-ment,resultinginafinaluncertaintyof0.1%.Thetriggerefficiency ofthe TISsample istaken fromsimulation.Its systematic uncer-taintyiscomputedfromthedifferencebetweentheTISefficiency taken from data and simulation for events which are triggered bothon the

Λ

+_c candidateandalsoon other tracks unassociated tothesignaldecay.Asaresult,asystematicuncertaintyof3.9%is assignedfortherelative trigger efficiencyoftheTIS sample, cor-respondingtoanuncertaintyof2.9%ontheratioofthebranching fractions.

The effect of the finite size of the simulated samples is as-sessedbyconsidering thepossiblevariationoftheefficiencywith weightedsamplesinabinof pTandrapidityofthe

Λ

0b candidate,

andthecorresponding systematicuncertaintyonthe efficiencyof thesignalornormalisationchannel,TISorTOSsample,isgivenby

σ



=



i



i

(

1

−



i

)

Niwi

/



i Niwi

,

(2)

wherefor each bin i, Ni is the number ofcandidates, wi is the

singleeventweight,and



i isthesingleeventefficiency.Thetotal

uncertaintyontherelativeefficiencyfortheTISandTOSsamples is1.2% and1.9%, respectively, corresponding to an uncertaintyof 1.3%ontheratioofthebranchingfractions.

Theuncertaintyduetotheremovalofcandidatesreconstructed withclonetracksandmultiplecandidatesisassessedbyapplying thesameproceduretosimulation,resultinginadifferenceof0.2%. Vetoes on the invariant mass of possible cross-feed back-groundsmaybiasthesignalmassdistributions.Anuncertaintyof 0.4%isdetermined bychangingthefitrangeofthenormalisation sampletobeginat5450 MeV

/

c2,insteadof5350 MeV

/

c2.

The agreement between data and simulation in the

Λ

c+

→

p K−

π

+ decayis alsotestedby comparing the Dalitz plot distri-butions. The normalisation sample is weighted in the m2

₍

_{p K}−

₎

versus m2

(

K−

π

+

)

plane. Due to the smaller sample size of the signal channel, weights obtained fromthe normalisation channel areappliedto thesignal. Theresultingprocedure rendersall dis-tributionsconsistentwithinonestatisticalstandarddeviation. The differencein theratioof branchingfractions is1.3% smallerthan thenominalresult,providing acorrection factorof0.984.An un-certainty of 0.2% is determined by using an alternative binning schemeandvaryingtheDalitz-plotweightsbytheirstatistical un-certainties.

The polarization ofthe

Λ

0_b particleshas beenmeasured tobe consistent withzero [25], but the weak decayof the

Λ

0_b baryon mayinduceapolarizationinthe

Λ

+_c system.Inthesimulation,it is assumedthat the

Λ

+_c particleis unpolarized,leading to a dif-ference in angular distributions between simulation and data. A possibleeffectduetothe

Λ

+c polarizationisassessedbyapplying

a weighting procedure to thedistribution of the

Λ

+c helicity

an-gle,whichisdefinedastheanglebetweenthe

Λ

+c flightdirection

inthe

Λ

0_b restframeandthedirectionofthep K− pairinthe

Λ

+_c

restframe.Thisweightisobtainedthroughacomparisonbetween theangulardistributionsinsimulationanddataforthesignaland the normalisation channels individually. Applying this weight to both the signal andthe normalisation channels doesnot change theefficiencywithrespecttoanyoftheotherpossibleangles,and leadstoachangeof1.1%intherelativeefficiencyfortheTOS sam-pleand1.4%fortheTISsample.Propagationoftheseuncertainties leads toacorrectionfactorof0.987ontheratioofthebranching fractions.An uncertaintyof0.3%isdetermined byusingan alter-nativebinningschemeandvaryingthesingle-candidateweightsby theirstatisticaluncertainties.

Simulateddataaregeneratedusingaphase-spacemodelforthe

Λ

_b0 decay, whichdoes not take into account possible resonances in the

Λ

+c p p

π

− system. Upon inspection, clearsignals from the

Σ

c0 and

Σ

c∗0 resonances are found,as described inSection 7. To

assess theeffect ofthese resonances, thesimulation is weighted toreproduce thedata.Weightsareapplied intwoinvariant mass dimensions,namelythe

Λ

+_c

π

−invariantmassandanother invari-ant mass of any two or three body combination. Among these weighting strategies,applyingweights inm

(Λ

+c

π

−

)

andm

(

p

π

−

)

(option 1) leads to the smallest

B

r, while weights in m

(Λ

+c

π

−

)

andm

(

p p

π

−

)

(option2)leadstothelargest

B

r.Acorrection

fac-tor iscomputed asthe averageof thecentral values ofthe ratio ofbranchingfractionsforthetwooptionsdividedbythenominal branchingfraction,withanuncertaintydeterminedbyhalfthe dif-ferencebetweenthetworatiosofbranchingfractions.Thisleadsto acorrectionfactorof1.041anda resultingsystematicuncertainty of1.8%.

UncertaintiesduetotheuseoftheBDTGaretestedby repeat-ing the BDTG training andselection procedure to the normalisa-tionchannelwithoutvariablesrelatedtothe p p pair;theratioof branchingfractionsisfoundtobeconsistent.

7. Resonancestructuresinthe

Λ

+c

π

−massspectrum

As the resonant structure of

Λ

0_b

→ Λ

+_cp p

π

− decays is unex-plored,the resonances in the

Λ

+_c

π

− system are studied.An un-binned maximum-likelihood fit ofthe

Λ

+c

π

− massis performed

for those candidates which pass all the selection criteria for the signal

Λ

_b0

→ Λ

+_c p p

π

− decays,to determineifthere areresonant contributions. In thiscasethe

Λ

0_b candidateis constrainedto its knownmass [15] whenobtainingthe

Λ

+_c

π

− invariantmass spec-trum.

Thesignal shapesofthe

Σ

c0 and

Σ

c∗0 resonances aregivenas

themodulussquaredoftherelativisticBreit–Wignerfunction[15],

|

BW

(

m

|

M0

,

0

)

|

2

=





1

/(

M20

−

m2

−

iM0

(

m

))





2

,

(3)

multiplied by m

(

m

)

, and convolved with a Gaussian resolution determined fromsimulation.Here, M0 istheknown valueof the

Σ

0

c or

Σ

c∗0 mass [15],m isthe

Λ

+c

π

− invariantmass, and



0 is themass-independentwidthoftheresonance,namely1.83 MeV

/

c2

for the

Σ

c0 and 15.3 MeV

/

c2 for the

Σ

c∗0 resonance. The

Fig. 2. InvariantmassoftheΛ+cπ−systemfromthedecayΛ0b→ Λ+cp pπ−.TheΣc0

andΣc∗0resonancesareindicated.Thefittothedataisshownasabluecontinuous

line,withthebackgroundcomponentshownasagreendottedline,theΣ0 c shape

shownasadashedredline,andtheΣ∗0

c shapeshownasadash-dottedmagenta

line.

(

m

)

= 

0

×



q q0



2L+1_M 0 m BL

(

q

,

q0

,

d

)

2

_,

₍₄₎

where L is the angular momentum in the resonance decay, q

is the momentum of the

Λ

+c baryon in the

Σ

(∗)0

c rest frame,

q0

≡

q

(

m

=

M0

)

and d stands for the size of the

Σ

c(∗)0

parti-cles.From parityandangularmomentumconservation,it follows that L

=

1.ThewidthalsodependsontheBlatt–Weisskopffactor

BL

(

q

,

q0

,

d

)

[26],wherethevalueofd issettobe1 fm (5GeV−1 in naturalunits).TheratioofwidthsoftheGaussianresolution func-tions forthe

Σ

c0 and

Σ

c∗0 resonances isfixed fromsimulationto

be1.96. Thebackgroundisdescribed withanempiricalthreshold function.ThefitshowninFig.2yields59

±

10

Λ

0_b

→ Σ

_c0p p decays

and104

±

17

Λ

0_b

→ Σ

_c∗0p p decays.

The relative efficiencies for the decays

Λ

0_b

→ Σ

0

cp p, with

Σ

0

c

→ Λ

+c

π

− and

Λ

0b

→ Σ

c∗0p p, with

Σ

c∗0

→ Λ

+c

π

− with

re-spect to

Λ

0_b

→ Λ

+cp p

π

− decays are determined with an

analo-gousprocedureasthatforthe

Λ

0_b

→ Λ

+cp p

π

− decaysrelativeto

the

Λ

0_b

→ Λ

+c

π

− decays,but withthetrigger samplescombined

duetolimitedsample size.The efficiencies are0

.

685

±

0

.

021 for the

Σ

0

c mode and 0

.

904

±

0

.

021 for the

Σ

c∗0 mode, relative to

Λ

0_b

→ Λ

+_c p p

π

−.

Many of the systematic uncertainties cancel out in the mea-surementof the ratioof branching fractions, withthe remaining systematic uncertainties stemming from the yield determination. Thevalueofd intheBlatt–Weisskopffactorisvariedbetween1.5 and0.5 fm,withthelargestvariationforeachresonancetakenas thesystematicuncertainty,resultingin3.4%forthe

Σ

_c0 resonance and1.9%forthe

Σ

c∗0 resonance.Thebackgroundshapeischanged

toa third-orderpolynomial, witha relativedifference of1.7% for the

Σ

c0 resonanceand10.6% forthe

Σ

c∗0 resonancetakenasthe

systematicuncertainty.Themassesandwidthsofthe

Σ

c(∗)0

reso-nancesareallowedtofloatwithin onestandarddeviationoftheir knownvalues [15],resultingina 3.8%differenceoftherawyield forthe

Σ

c0 resonanceand2.2%difference forthe

Σ

c∗0 resonance.

Alluncertainties intherelative efficiencycancel,exceptforthose relatedtotheweightingduetoresonantstructuresinthe

Λ

+_c

π

− system.Thescalingfactorof1.041,withanuncertaintyof1.8%on therelativeefficiency,whichisshowninTable1,isthereforeused hereaswell.Theresultingratiosofbranchingfractionsare

B

(Λ

0_b

→ Σ

_c0p p

)

×

B

(Σ

_c0

→ Λ

+_c

π

−

)

B

(Λ

0_b

→ Λ

+c p p

π

−

)

=

0

.

089

±

0

.

015

±

0

.

006

,

B

(Λ

0_b

→ Σ

_c∗0p p

)

×

B

(Σ

_c∗0

→ Λ

+_c

π

−

)

B

(Λ

0_b

→ Λ

+c p p

π

−

)

=

0

.

119

±

0

.

020

±

0

.

014

,

wherethefirstuncertaintyisstatisticalandthesecondis system-atic.

8. Searchfordibaryonresonances

The existence of dibaryon resonances,

D

_c+

→

p

Σ

c0, is

investi-gated in the

Λ

+c

π

−p mass spectrum of background-subtracted

data. The full m

(Λ

+_c

π

−

)

spectrum is considered, while the sig-nal regions of

Σ

c0 and

Σ

c∗0 resonances are defined by the

ranges 2450

<

m

(Λ

+c

π

−

) <

2458 MeV

/

c2 and2488

<

m

(Λ

+c

π

−

)

<

2549 MeV

/

c2_{,respectively. Thebackground issubtracted withthe}

sPlot technique [27]. No peaking structures are observed in the

distributions showninFig.3.Thetwo-dimensionaldistributionof

m

(Λ

+cp

π

−

)

versusm

(Λ

+c

π

−

)

hasbeencheckedanddoesnot

ex-hibitanyclearstructure.

9. Conclusion

Thefirstobservationofthedecay

Λ

_b0

→ Λ

+c p p

π

−ispresented.

Theratioofthebranchingfractionsusingthedecay

Λ

_b0

→ Λ

_c+

π

− asthenormalisationchannelismeasuredtobe

B

(Λ

0_b

→ Λ

+c p p

π

−

)

B

(Λ

_b0

→ Λ

+c

π

−

)

=

0

.

0540

±

0

.

0023

±

0

.

0032

,

using data corresponding to an integrated luminosity of 3 fb−1 collectedduring2011and2012withtheLHCb detector. Contribu-tionsfromthe

Σ

c

(

2455

)

0and

Σ

c∗

(

2520

)

0resonancesareobserved,

and the ratios of their branching fractions with respect to the

Λ

0_b

→ Λ

+cp p

π

− decaysaremeasuredtobe

B

(Λ

0_b

→ Σ

_c0p p

)

×

B

(Σ

_c0

→ Λ

+_c

π

−

)

B

(Λ

0_b

→ Λ

+c p p

π

−

)

=

0

.

089

±

0

.

015

±

0

.

006

,

B

(Λ

0_b

→ Σ

_c∗0p p

)

×

B

(Σ

_c∗0

→ Λ

+_c

π

−

)

B

(Λ

0_b

→ Λ

+c p p

π

−

)

=

0

.

119

±

0

.

020

±

0

.

014

.

In all ofthe above results, the first uncertainty is statisticaland thesecondissystematic.

The massspectraofthe

Λ

+cp

π

− finalstate are alsoinspected

forpossibledibaryonresonances,butnoevidenceofpeaking struc-turesisobserved.

Acknowledgements

We express our gratitude to our colleagues in the CERN ac-celerator departments for the excellent performance of the LHC. WethankthetechnicalandadministrativestaffattheLHCb insti-tutes. WeacknowledgesupportfromCERNandfromthenational agencies:CAPES,CNPq,FAPERJandFINEP(Brazil);MOSTandNSFC (China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN (Italy); NWO (TheNetherlands);MNiSW andNCN(Poland); MEN/IFA (Romania); MinES and FASO (Russia); MinECo (Spain); SNSF andSER (Switzerland); NASU(Ukraine); STFC (United King-dom); NSF(USA). We acknowledge thecomputingresources that are provided by CERN, IN2P3 (France), KIT andDESY (Germany), INFN (Italy),SURF (TheNetherlands), PIC (Spain), GridPP (United Kingdom), RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH(Romania),CBPF(Brazil),PL-GRID(Poland)andOSC(USA).

Fig. 3. Background-subtractedmassspectrumoftheΛ+cπ−p systemfromthedecayΛ0b→ Λ+cp pπ−in(a)thefullΛ+cπ−massspectrum,(b)thesignalregionoftheΣc0

resonance,and(c)thesignalregionoftheΣc∗0resonance.Inallfigures,theblackpointsaredataandtheredpointsare simulatedeventswheretheΛ0bbaryondecays

totheΛ+cp pπ− finalstate(a)basedonauniform-phase-spacemodel,(b)throughtheΣc0resonanceand(c)throughtheΣc∗0resonance.Noevidentpeakingshapesare

visible.

We are indebted to the communities behind the multiple open-sourcesoftwarepackagesonwhichwedepend. Individualgroups or members have received support from AvH Foundation (Ger-many),EPLANET,Marie Skłodowska-CurieActions andERC (Euro-peanUnion),ANR,Labex P2IOandOCEVU,andRégion Auvergne-Rhône-Alpes (France),Key Research Program of Frontier Sciences ofCAS,CASPIFI,andtheThousandTalentsProgram(China),RFBR, RSFandYandexLLC(Russia),GVA,XuntaGalandGENCAT(Spain), HerchelSmithFund,theRoyalSociety,theEnglish-SpeakingUnion andtheLeverhulmeTrust(UnitedKingdom).

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LHCbCollaboration

R. Aaij

43

,

B. Adeva

39

,

M. Adinolfi

48

,

Z. Ajaltouni

5

,

S. Akar

59

,

P. Albicocco

19

,

J. Albrecht

10

,

F. Alessio

40

,

M. Alexander

53

,

A. Alfonso Albero

38

,

S. Ali

43

,

G. Alkhazov

31

,

P. Alvarez Cartelle

55

,

A.A. Alves Jr

59

,

S. Amato

2

,

S. Amerio

23

,

Y. Amhis

7

,

L. An

3

,

L. Anderlini

18

,

G. Andreassi

41

,

M. Andreotti

17

,

g

,

J.E. Andrews

60

,

R.B. Appleby

56

,

F. Archilli

43

,

P. d’Argent

12

,

J. Arnau Romeu

6

,

A. Artamonov

37

,

M. Artuso

61

,

E. Aslanides

6

,

M. Atzeni

42

,

G. Auriemma

26

,

S. Bachmann

12

,

J.J. Back

50

,

S. Baker

55

,

V. Balagura

7

,

b

,

W. Baldini

17

,

A. Baranov

35

,

R.J. Barlow

56

,

S. Barsuk

7

,

W. Barter

56

,

F. Baryshnikov

32

,

V. Batozskaya

29

,

V. Battista

41

,

A. Bay

41

,

J. Beddow

53

,

F. Bedeschi

24

,

I. Bediaga

1

,

A. Beiter

61

,

L.J. Bel

43

,

N. Beliy

63

,

V. Bellee

41

,

N. Belloli

21

,

i

,

K. Belous

37

,

I. Belyaev

32

,

40

,

E. Ben-Haim

8

,

G. Bencivenni

19

,

C. Betancourt

42

,

F. Betti

15

,

40

,

M.O. Bettler

49

,

M. van Beuzekom

43

,

Ia. Bezshyiko

42

,

S. Bifani

47

,

P. Billoir

8

,

A. Birnkraut

10

,

A. Bizzeti

18

,

u

,

M. Bjørn

57

,

T. Blake

50

,

F. Blanc

41

,

S. Blusk

61

,

V. Bocci

26

,

O. Boente Garcia

39

,

T. Boettcher

58

,

A. Bondar

36

,

w

,

N. Bondar

31

,

S. Borghi

56

,

40

,

M. Borisyak

35

,

M. Borsato

39

,

40

,

F. Bossu

7

,

M. Boubdir

9

,

T.J.V. Bowcock

54

,

E. Bowen

42

,

C. Bozzi

17

,

40

,

S. Braun

12

,

M. Brodski

40

,

J. Brodzicka

27

,

D. Brundu

16

,

E. Buchanan

48

,

C. Burr

56

,

A. Bursche

16

,

J. Buytaert

40

,

W. Byczynski

40

,

S. Cadeddu

16

,

H. Cai

64

,

R. Calabrese

17

,

g

,

R. Calladine

47

,

M. Calvi

21

,

i

,

M. Calvo Gomez

38

,

m

,

A. Camboni

38

,

m

,

P. Campana

19

,

D.H. Campora Perez

40

,

L. Capriotti

56

,

A. Carbone

15

,

e

,

G. Carboni

25

,

R. Cardinale

20

,

h

,

A. Cardini

16

,

P. Carniti

21

,

i

,

L. Carson

52

,

K. Carvalho Akiba

2

,

G. Casse

54

,

L. Cassina

21

,

M. Cattaneo

40

,

G. Cavallero

20

,

h

,

R. Cenci

24

,

p

,

D. Chamont

7

,

M.G. Chapman

48

,

M. Charles

8

,

Ph. Charpentier

40

,

G. Chatzikonstantinidis

47

,

M. Chefdeville

4

,

S. Chen

16

,

S.-G. Chitic

40

,

V. Chobanova

39

,

M. Chrzaszcz

40

,

A. Chubykin

31

,

P. Ciambrone

19

,

X. Cid Vidal

39

,

G. Ciezarek

40

,

P.E.L. Clarke

52

,

M. Clemencic

40

,

H.V. Cliff

49

,

J. Closier

40

,

V. Coco

40

,

J. Cogan

6

,

E. Cogneras

5

,

V. Cogoni

16

,

f

,

L. Cojocariu

30

,

P. Collins

40

,

T. Colombo

40

,

A. Comerma-Montells

12

,

A. Contu

16

,

G. Coombs

40

,

S. Coquereau

38

,

G. Corti

40

,

M. Corvo

17

,

g

,

C.M. Costa Sobral

50

,

B. Couturier

40

,

G.A. Cowan

52

,

D.C. Craik

58

,

A. Crocombe

50

,

M. Cruz Torres

1

,

R. Currie

52

,

C. D’Ambrosio

40

,

F. Da Cunha Marinho

2

,

C.L. Da Silva

73

,

E. Dall’Occo

43

,

J. Dalseno

48

,

A. Danilina

32

,

A. Davis

3

,

O. De Aguiar Francisco

40

,

K. De Bruyn

40

,

S. De Capua

56

,

M. De Cian

41

,

J.M. De Miranda

1

,

L. De Paula

2

,

M. De Serio

14

,

d

,

P. De Simone

19

,

C.T. Dean

53

,

D. Decamp

4

,

L. Del Buono

8

,

B. Delaney

49

,

H.-P. Dembinski

11

,

M. Demmer

10

,

A. Dendek

28

,

D. Derkach

35

,

O. Deschamps

5

,

F. Dettori

54

,

B. Dey

65

,

A. Di Canto

40

,

P. Di Nezza

19

,

S. Didenko

69

,

H. Dijkstra

40

,

F. Dordei

40

,

M. Dorigo

40

,

A. Dosil Suárez

39

,

L. Douglas

53

,

A. Dovbnya

45

,

K. Dreimanis

54

,

L. Dufour

43

,

G. Dujany

8

,

P. Durante

40

,

J.M. Durham

73

,

D. Dutta

56

,

R. Dzhelyadin

37

,

M. Dziewiecki

12

,

A. Dziurda

40

,

A. Dzyuba

31

,

S. Easo

51

,

U. Egede

55

,

V. Egorychev

32

,

S. Eidelman

36

,

w

,

S. Eisenhardt

52

,

U. Eitschberger

10

,

R. Ekelhof

10

,

L. Eklund

53

,

S. Ely

61

,

A. Ene

30

,

S. Escher

9

,

S. Esen

12

,

H.M. Evans

49

,

T. Evans

57

,

A. Falabella

15

,

N. Farley

47

,

S. Farry

54

,

D. Fazzini

21

,

40

,

i

,

L. Federici

25

,

G. Fernandez

38

,

P. Fernandez Declara

40

,

A. Fernandez Prieto

39

,

F. Ferrari

15

,

L. Ferreira Lopes

41

,

F. Ferreira Rodrigues

2

,

M. Ferro-Luzzi

40

,

S. Filippov

34

,

R.A. Fini

14

,

M. Fiorini

17

,

g

,

M. Firlej

28

,

C. Fitzpatrick

41

,

T. Fiutowski

28

,

F. Fleuret

7

,

b

,

M. Fontana

16

,

40

,

F. Fontanelli

20

,

h

,

R. Forty

40

,

V. Franco Lima

54

,

M. Frank

40

,

C. Frei

40

,

J. Fu

22

,

q

,

W. Funk

40

,

C. Färber

40

,

E. Gabriel

52

,

A. Gallas Torreira

39

,

D. Galli

15

,

e

,

S. Gallorini

23

,

S. Gambetta

52

,

M. Gandelman

2

,

P. Gandini

22

,

Y. Gao

3

,

L.M. Garcia Martin

71

,

B. Garcia Plana

39

,

J. García Pardiñas

42

,

J. Garra Tico

49

,

L. Garrido

38

,

D. Gascon

38

,

C. Gaspar

40

,

L. Gavardi

10

,

G. Gazzoni

5

,

D. Gerick

12

,

E. Gersabeck

56

,

M. Gersabeck

56

,

T. Gershon

50

,

Ph. Ghez

4

,

S. Gianì

41

,

V. Gibson

49

,

O.G. Girard

41

,

L. Giubega

30

,

K. Gizdov

52

,

V.V. Gligorov

8

,

D. Golubkov

32

,

A. Golutvin

55

,

69

,

A. Gomes

1

,

a

,

I.V. Gorelov

33

,

C. Gotti

21

,

i

,

E. Govorkova

43

,

J.P. Grabowski

12

,

R. Graciani Diaz

38

,

L.A. Granado Cardoso

40

,

E. Graugés

38

,

E. Graverini

42

,

G. Graziani

18

,

A. Grecu

30

,

R. Greim

43

,

P. Griffith

16

,

L. Grillo

56

,

L. Gruber

40

,

B.R. Gruberg Cazon

57

,

O. Grünberg

67

,

E. Gushchin

34

,

Yu. Guz

37

,

40

,

T. Gys

40

,

C. Göbel

62

,

T. Hadavizadeh

57

,

C. Hadjivasiliou

5

,

G. Haefeli

41

,

C. Haen

40

,

S.C. Haines

49

,

B. Hamilton

60

,

X. Han

12

,

T.H. Hancock

57

,

S. Hansmann-Menzemer

12

,

N. Harnew

57

,

S.T. Harnew

48

,

C. Hasse

40

,

M. Hatch

40

,

J. He

63

,

M. Hecker

55

,

K. Heinicke

10

,

A. Heister

9

,

K. Hennessy

54

,

L. Henry

71

,

E. van Herwijnen

40

,

M. Heß

67

,

A. Hicheur

2

,

D. Hill

57

,

P.H. Hopchev

41

,

W. Hu

65

,

W. Huang

63

,

Z.C. Huard

59

,

W. Hulsbergen

43

,

T. Humair

55

,

M. Hushchyn

35

,

D. Hutchcroft

54

,

P. Ibis

10

,

M. Idzik

28

,

P. Ilten

47

,

K. Ivshin

31

,

R. Jacobsson

40

,

J. Jalocha

57

,

E. Jans

43

,

A. Jawahery

60

,

F. Jiang

3

,

M. John

57

,

D. Johnson

40

,

C.R. Jones

49

,

C. Joram

40

,

B. Jost

40

,

N. Jurik

57

,

S. Kandybei

45

,

M. Karacson

40

,

J.M. Kariuki

48

,

S. Karodia

53

,

N. Kazeev

35

,

M. Kecke

12

,

F. Keizer

49

,

M. Kelsey

61

,

M. Kenzie

49

,

T. Ketel

44

,

E. Khairullin

35

,

B. Khanji

12

,

C. Khurewathanakul

41

,

K.E. Kim

61

,

T. Kirn

9

,

S. Klaver

19

,

K. Klimaszewski

29

,

T. Klimkovich

11

,

S. Koliiev

46

,

M. Kolpin

12

,

R. Kopecna

12

,

P. Koppenburg

43

,

S. Kotriakhova

31

,

M. Kozeiha

5

,

L. Kravchuk

34

,

M. Kreps

50

,

F. Kress

55

,

P. Krokovny

36

,

w

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W. Krupa

28

,

W. Krzemien

29

,

W. Kucewicz

27

,

l

,

M. Kucharczyk

27

,

V. Kudryavtsev

36

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w

,

A.K. Kuonen

41

,

T. Kvaratskheliya

32

,

40

,

D. Lacarrere

40

,

G. Lafferty

56

,

A. Lai

16

,

G. Lanfranchi

19

,

C. Langenbruch

9

,

T. Latham

50

,

C. Lazzeroni

47

,

R. Le Gac

6

,

A. Leflat

33

,

40

,

J. Lefrançois

7

,

R. Lefèvre

5

,

F. Lemaitre

40

,

O. Leroy

6

,

T. Lesiak

27

,

B. Leverington

12

,

P.-R. Li

63

,

T. Li

3

,

Z. Li

61

,

X. Liang

61

,

T. Likhomanenko

68

,

R. Lindner

40

,

F. Lionetto

42

,

V. Lisovskyi

7

,

X. Liu

3

,

D. Loh

50

,

A. Loi

16

,

I. Longstaff

53

,

J.H. Lopes

2

,

D. Lucchesi

23

,

o

_,

_{M. Lucio Martinez}

39

_,

_{A. Lupato}

23

_,

_{E. Luppi}

17

,

g

_,

_{O. Lupton}

40

_,

_{A. Lusiani}

24

_,