First Measurements of Heavy Flavor Production
√
at s = 13 TeV
Bruno Galinhas
LIP-CMS
May 25, 2017
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IDPASC Workshop - Braga 2017
Motivation
Why heavy flavor?
Test quantum chromodynamics (QCD)
First production measurements at LHC record energy: probe high pT
Important reference for heavy-ion collisions
Baseline for measurements and searches of rarer decays
Important ingredient for B(Bs0 → µ+ µ− ) =
in search for new physics
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Ns fu u
+
Nu fs s B(B )
IDPASC Workshop - Braga 2017
Measurements
How?
Differential production cross section of Bs0 , B 0 , and B +
Fragmentation fraction ratios fs /fu and fs /fd
fs is the probability that the b̄ quark is bound to an s quark
fu + fd + fs + fc + fbaryon = 1
Decay channels used:
Bs0 → J/ψ φ → µµ K + K −
B 0 → J/ψ K ∗0 → µµ K + π −
B + → J/ψ K + → µµ K +
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Event selection
Data from pp collisions in Run II (2015) with L = 2.71 fb−1
Trigger: J/ψ displaced from the pp interaction point
Selection:
Muons: pT (µ) > 4.0 GeV, |η(µ)| < 2.4, SoftMuonID = True
|Mµµ − MJ/ψ | < 150 MeV, pT (J/ψ) > 10 GeV, dimuon vertexing
probability > 10 %
Tracks: pT > 0.7 GeV, |η| < 2.5, χ2 /ndf < 5.0,
strip hits + pixel hits > 5
B candidates: vertexing probability > 20 %, (Lxy /σxy ) > 3.0,
cos α > 0.996
Bs0 candidates: |MKK − Mφ | < 10 MeV and |MK π − MK ∗0 | > 50 MeV
B 0 candidates: |MK π − MK ∗0 | < 50 MeV and |MKK − Mφ | > 10 MeV
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IDPASC Workshop - Braga 2017
Signal yield extraction
Signal extracted with an extended unbinned maximum likelihood fit to
the invariant mass of the B candidates.
Model:
Signal: sum of two gaussians
Combinatorial background: exponential
Other components:
Mis-id Kπ signal: B 0 channel
Partially reconstructed decays: B + channel
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IDPASC Workshop - Braga 2017
Overall efficiency (Bs0 )
Bs0 Overall efficiency: Acceptance, reconstruction and trigger
efficiencies as function of pT (B) and |y |(B)
Calculated using MC samples, dedicated to each decay channel
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Differential production cross section
dσ(pp→B + X )
B
dpT
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=
B
Nsignal
B
2 u B(B + →J/ψK + )B(J/ψ→µ+ µ− ) L ∆pT
IDPASC Workshop - Braga 2017
Fragmentation fraction ratios
Fragmentation fraction ratio:
Ratio
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fs
fu
fs
fu
=
B(B + →J/ψ K + )
εu
Ns
Nu B(Bs0 →J/ψ φ)B(φ→K + K − ) εs
as a funtion of pT and |y |
IDPASC Workshop - Braga 2017
Fragmentation fraction ratios
Fragmentation fraction ratio:
Ratio
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fs
fd
fs
fd
=
Ns B(B 0 →J/ψ K ∗0 )B(K ∗0 → K + π − ) εd
Nd
εs
B(Bs0 →J/ψ φ)B(φ→K + K − )
as a funtion of pT and |y |
IDPASC Workshop - Braga 2017
Summary
First measurements of differential production cross section of
Bs0 , B 0 , and B + at 13 TeV
Reaching a pT above 100 GeV
First measurements of fs /fu and fs /fd preformed by CMS
Established no kinematic dependence
These measurements are important to test QCD in the high pT
regime, and allow an improved measurement of B(Bs0 → µ+ µ− )
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IDPASC Workshop - Braga 2017
Plans
Current focus is on carrying out systematic studies of the B → µµ BF
measurement,
LIP is reponsible for the fs /fd ingredient (dominant systematic source)
in addition to Bs → µµ paper, considering standalone publication of
cross sections and fragmentation fraction ratios
Future work:
there are additional ingredients of the B → µµ analysis we can improve
in addition to the BF, we are interested in exploring the effective
lifetime, providing complementary sensitivity to NP
trigger is a critical ingredient
other interesting rare decay searches, e.g. τ → µµµ , H → J/ψ + γ
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IDPASC Workshop - Braga 2017
Thank you!
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IDPASC Workshop - Braga 2017
Back-up slides
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IDPASC Workshop - Braga 2017
B to mumu
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IDPASC Workshop - Braga 2017
Datasets and MC samples
Datasets used:
dataset=/Charmonium/Run2015C-PromptReco-v1/AOD
dataset=/Charmonium/Run2015D-PromptReco-v3/AOD
dataset=/Charmonium/Run2015D-PromptReco-v4/AOD
Filtered with json file:
Cert 246908260627 13TeV PromptReco Collisions15 25ns JSON MuonPhys.txt
Integrated luminosity of L = 2.71 fb−1 and total centre of mass
√
energy s = 13 TeV
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Datasets and MC Samples
MC Samples for Bs0 → J/ψ φ(K + K − ):
dataset=/BsToJpsiPhiV2 BFilter TuneCUEP8M1 13TeV-pythia8evtgen/RunIISpring15DR74-Asympt25ns MCRUN2 74 V9 ext1v1/AODSIM
dataset=/BsToJpsiPhi BMuonFilter TuneCUEP8M1 13TeV-pythia8evtgen/RunIISpring15DR74-Asympt25nsRaw MCRUN2 74 V9-v1/AODSIM
MC Samples for B 0 → J/ψ K ∗0 (K + π − ):
dataset=/BdToJpsiKstarV2 BFilter TuneCUEP8M1 13TeV-pythia8evtgen/RunIISpring15DR74-Asympt25ns MCRUN2 74 V9v1/AODSIM
dataset=/BdToJpsiKstarV2 BMuonFilter TuneCUEP8M1 13TeV-pythia8evtgen/RunIISpring15DR74-Asympt25ns MCRUN2 74 V9-v1/AODSIM
MC Samples for B + → J/ψ K + :
dataset=/BuToJpsiKV2 BFilter TuneCUEP8M1 13TeV-pythia8evtgen/RunIISpring15DR74-Asympt25ns MCRUN2 74 V9-v1/AODSIM
dataset=/BuToJpsiKV2 BMuonFilter TuneCUEP8M1 13TeV-pythia8evtgen/RunIISpring15DR74-Asympt25ns MCRUN2 74 V9-v1/AODSIM
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Branching fractions
PDG values:
B(Bs0 → J/ψ φ) = (1.08 ± 0.09) × 10−3
B(φ → K + K − ) = (48.9 ± 0.5) × 10−2
B(B + → J/ψ K + ) = (1.026 ± 0.031) × 10−3
B(B 0 → J/ψ K ∗0 ) = (1.32 ± 0.06) × 10−3
B(K ∗0 → K + π − ) = (66.503 ± 0.014) × 10−2
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Efficiencies of Bs0 , B 0 , and B +
Efficiencies as function of pT
Efficiencies as function of |y |
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Efficiency ratios
Ratio
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εu
εs
as a funtion of pT and |y |
IDPASC Workshop - Braga 2017
Efficiency ratios
Ratio
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εd
εs
as a funtion of pT and |y |
IDPASC Workshop - Braga 2017
Efficiency ratios
Ratio
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εu
εd
as a funtion of pT and |y |
IDPASC Workshop - Braga 2017
Fragmentation fraction ratios
Ratio
fd
fu
Integral measurement:
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as a funtion of pT and |y |
fd
fu
= 0.915 ± 0.006 (stat.) ± 0.052 (syst.)
IDPASC Workshop - Braga 2017
K π swap
Count the number of K π true
signal and K π swapped signal
Nswapped
Ntrue
= 0.13
Fit the swapped component
with two gaussians
Add it to the nominal fit of B 0
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IDPASC Workshop - Braga 2017