b physics and quarkonia at cms
DESCRIPTION
B Physics and Quarkonia at CMS. ICNFP 2014 Kolymbari , Crete 6 August 2014. Claudia-Elisabeth Wulz CMS Collaboration Institute of High Energy Physics, Vienna. Overview. Selected recent results: - PowerPoint PPT PresentationTRANSCRIPT
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B Physics and Quarkonia at CMS
Claudia-Elisabeth WulzCMS CollaborationInstitute of High Energy Physics, Vienna
ICNFP 2014Kolymbari, Crete 6 August 2014
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ICNFP, Aug. 2014C.-E. Wulz 2
Overview
Selected recent results: - CP-violating phase fs and decay width difference DGs of Bs with
Bs -> J/ y f(1020)
- Production cross sections- J/ y and y(2S) prompt double-differential
- Polarization- J/ , y y(2S),ϒ(1S), ϒ(2S),ϒ(3S)
CMS PAS BPH-13-012
CMS PAS BPH-14-001
All CMS public B physics results:
https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsBPH
PLB 727 (2013) 381
PRL 110 (2013) 081802
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Bs -> J/ (μy +μ-)f(K+K-)
Decay channel: Bs -> J/ (μy +μ-)f(K+K-)Bs-Bs mixing -> time-dependent, flavour-tagged analysisData: √s = 8 TeV, Lint = 20 fb-1, 49000 reconstructed Bs decays
Weak phase from interference of direct decays and decays from mixing, and decay width difference of light and heavy Bs mass eigenstates:
_
+ newphysics?
+ newphysics?
Bs
Bs J/ y f
fD
fM -fD_
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Angular analysisTime-dependent, angular analysis to disentangle CP-odd and CP-even final states:- Measure decay angles Θ(θT,φT,ψT) and proper decay length of
Bs
PRD 87 (2013) 112010 - LHCb
a parameter set: ΔΓs, ϕs, cτ, IA0I2, IASI2, IATI2, δII, δST, δT
bi and ci depend on ϕs
Extended maximum likelihood fit with signal model used to extract parameters.
Signal model
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Trigger: displaced J/y, optimized for b hadrons • 2 muons with pT(μ) > 4 GeV, pT (μμ) > 6.9 GeV• Mass window for μμ : [2.9,3.3] GeV• Common decay vertex, Lxy/σxy > 3, dca3D > 0.5 cm• Vertex fit probability > 15%
Offline selection:• pT(μ+), pT(μ-) > 4 GeV, IημI < 2.1 • Dimuons from common vertex from Kalman fit• J/y mass constraint: Imμ+μ-– MJ/ψI < 150 MeV• pT(K+), pT(K-) > 0.7 GeV• ϕ mass constraint: ImK+K-– MϕI < 10 MeV
Bs (μμKK) reconstruction by combined kinematic and vertex fit:• c2 vertex fit probability > 2%• Mass within [5.24, 5.49] GeV• Selected primary vertex: closest to Bs (minimal angle between
flight direction and momentum of Bs)
Event selection and Bs reconstruction
CMS PAS BPH-13-012
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Main background: non-prompt J/y from b hadronsLifetime and angular resolution and efficiencies: from simulation
• Angular efficiency: modeled by 3D-function of decay angles• Angular resolution: not in nominal fit, but included as
systematic uncertainty• Proper decay time efficiency: not in nominal fit, flat in fitting
range [0.02,0.3] cm, variations included as systematic uncertainty
• Proper decay time resolution (70 ps or 21 μm): per-event uncertainty from Bs vertex finding + scale factor κ(cτ) taking account the difference with respect to the resolution
Background, efficiencies, resolution
CMS PAS BPH-13-012
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Flavor of Bs at production time determined by tagging e or μ on opposite side and considering its charge
Tagging performance optimized by maximizing tagging power Ptag = εtag(1-2ω)2 separately for e and μ (ω … mistag fraction)
εtag measured from data, using self-tagging channel B+ -> J/ψ K+, and checked by simulation with B+ -> J/y K+ and Bs
-> J/y K*0 events
Flavor tagging
CMS PAS BPH-13-012
Combined average tagging performance:ω = (32.3 ± 0.3)%, εtag = (7.67 ± 0.04)%, Ptag = (0.97 ± 0.3)%
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Systematic uncertainties
CMS PAS BPH-13-012
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Multi-dimensional maximum likelihood fit applied with tagged signal model, Gaussian constraint on Δms to PDG value
Fit range:Bs mass in [5.24, 5.49] GeVct in [0.02, 0.3] cm
Fit results
CMS PAS BPH-13-012
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ϕs = - 0.03 ± 0.11 (stat.) ± 0.03 (syst.) rad
ΔΓs = 0.096 ± 0.014 (stat.) ± 0.007 (syst.) ps-1
Results on Φs, ΔΓs
CMS PAS BPH-13-012
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- Quarkonia cross sections and polarization
Heavy quarkonia interesting to understand hadron formation. S-wave vector quarkonia formed from heavy qq pairs created as:color singlet (CS) 3S1
[1] or one of 3 color octets (CO) 1S0[8], 3S1
[8], 3PJ
[8] -> similar cross section shapes, but different polarizations.Experimental situation on polarization not clear up to now, cross sections only measured in lower pT range.
_
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Polarization of JPC = 1–– quarkonium states measured through angular distribution of dileptons from J/y or ϒ decay
Quarkonium polarization
Quarkonium rest frame
production plane
yx
z
ϑ
φ
ℓ +
Quantization axis z
EPJC C69 (2010) 657
PRD 16 (1977) 2219PRD 19 (1979) 207
TransverseJZ = ±1
LongitudinalJZ = 0
Frame-invariant:
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- Selection of prompt charmonia
l = Lxy . mψ(nS)/pT
Prompt charmonia distinguished from B-hadron decays through μμ pseudo-proper decay length l (Lxy ... most probable transverse decay length)
Yield: extended unbinned maximum-likelihood fit to 2D M-l distribution
EPJC 71(2011) 1575
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Single μ efficiencies, correlations and acceptance
Single muon efficiencies: tag&probe method
ρ: trigger-induced muon pair correlations
Acceptance: polarization-dependentUnpolarized scenario used for cross section measurements (measured value λϑ ≈ 0.1)
CMS-PAS-BPH-14-001
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- J/ψ and ψ(2S) production
ICNFP, Aug. 2014
CMS PAS BPH-14-001
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J/y and y(2s) polarizations, 7 TeVϒ(1s), ϒ(2s), ϒ(3s) polarizations, 7 TeV
ψ(nS) and ϒ(nS) polarizationsPLB 727(2013) 381
ϒ(3S)
ϒ(2S)
ϒ(1S)
ψ(2S)J/ψ
- Full angular decay distributions measured in 3 frames and frame-independently- Continuum background from sidebands in the invariant mass distribution- Non-prompt charmonium contributions removed using decay length
PRL 110 (2013) 081802
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J/ψ and ψ(2S) polarization
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J/ψ and ψ(2S) polarization
- No strong polarization- No strong pT dependence- Similar in other frames and for other polarization parameters- NLO NRQCD predictions (no feed-down for J/y) do not agree with
data
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ϒ(nS) polarization
- No strong polarization- No strong pT or y dependence
PRL 110 (2013) 081802
PRL 108 (2012) 151802
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ψ(2S), ϒ(3S) production versus NRQCD
- y(2S), ϒ(3S) assumed to be feed-down free; cb(3P) feed-down to (3S) neglected
- Unpolarized 1S0[8] component dominates quarkonium
production
PLB 727 (2013) 381PRL 110 (2013) 081802
arXiv:1403.3970
JHEP 02 (2012) 011PRD 87 (2013) 052004CMS-PAS-BPH-12-006
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• CMS has measured CP-violating phase fs and decay width difference DGs of Bs with Bs -> J/ (μμ) y f(KK) at √s = 7 TeV, in agreement with standard model.
• CMS has measured J/y and y(2S) prompt double-differential cross sections in several rapidity bins at √s = 7 TeV.
• CMS has measured polarization of JPC = 1–– quarkonium states through angular distribution of dileptons from J/y or ϒ decay. No strong polarization is seen. Unpolarized 1S0
[8] component dominates quarkonium production.
• CMS is preparing to take new B physics data at √s = 13 TeV in 2015.
Conclusions on new CMS results
ICNFP, Aug. 2014
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BACKUP
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Charmonium spectrum
cc_
1--
non-prompt(b-hadrons)
directly produced
ψ’
χc2χc1
J/ψ
non-prompt(b-hadrons)
directly producedψ‘
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Bottomonium spectrum
1--
bb
_
1--
χbJ(3P)
χbj(2P) χbj(1P)
(2S,3S)
directly produced(1S)
χbj(3P)χbj(2P)
(3S)
directly produced(2S)
χbj(3P)
directly produced(3S)
χbj(3P)
35-45%
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Pseudo-proper delay length
l = Lxy· mψ(nS)/pTEur.Phys.J.C71:1575,2011
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Hadron formation and NRQCD NRQCD is an effective field theory that factorizes quarkonium production in two steps:1) production of the initial quark-antiquark pair (perturbative QCD)2) hadronization of the quark pair into a bound quarkonium state (non-perturbative QCD)
NRQCD predicts the existence of intermediate color-octet (CO) states in nature, that subsequently evolve into physical color-singlet (CS) quarkonia by non-perturbative emission of soft gluons.
Quantum numbers of the heavy quark pairS, L, J = spin, orbital and total ang. momentum
possibly colored qq pair of any possible 2S+1LJ quantum numbers
1) perturbative phase
_
green
antiblue
2) non-perturbative evolutionto the observed bound stateQuantum numbers change!
redquarkonium ( )
antired
Cartoon
by P. F
accioli = 2S+1LJ
[C] , C = 1,8