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QCD 与强子物理研讨会, 2010 年 8 月 4 - 10 日,威海
Prospects of Flavor Physics at the LHC
高原宁清华大学高能物理研究中心
2010/8/6 1Y. Gao, Prospects of flavor physics at the LHC
Outline(very selective view of the field)
• Early results from the LHC experiments
• LHC as a B factory
• Remarks on flavor physics
• Status and prospects - CKM matrix - Bs mixing - Rare decays
• Conclusion
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 2
LHC is running…
• ~400 nb-1/experiment delivered to ATLAS, CMS , LHCb• Date collected with high efficiencies (> 90%) • Much more underway…
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 3
LHCb operation
Quarkonia production
• Signals seen from data !
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 4
Quarkonia production
• J/ in central region
• J/ in forward region
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 5
CMS preliminary : (4≤pT≤30GeV/c and |y| <2.4)
BR(J/ψ→µ+µ−)·σ(pp→J/ψ + X) = (289.1 ± 16.7(stat) ± 60.1(syst)) nb
LHCb preliminary : (pT≤10GeV/c and 2.5<y <4)
σ(pp→J/ψ + X) = (7.65 ± 0.19(stat) ± 1.10(syst) +0.87
-1.27 ) b
Data favor neither color singlet nor color octet model.
Quarkonia production
• 1s, 2s and 3s→μ+μ-
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 6
σ(pp →Υ(1S)X)·B(Υ(1S)→µ+ µ−)=(8.3±0.5±0.9±1.0)nb(Assuming no polarization and integrated over |y| <2.0)
bb cross-section • bb in central region
• bb in forward region
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 7
CMS preliminary : (4≤pT≤30GeV/c and |y| <2.4)
BR(J/ψ→µ+µ−)· σ(pp→bX→ J/ψX’) = (56.1 ± 5.5(stat) ± 7.2(syst) )nb
LHCb preliminary : (pT≤10GeV/c and 2.5<y <4)
σ(pp→ bX→ J/ψX’) = (0.81 ± 0.06(stat) ± 0.13(syst) ) b
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-
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bb cross-section • bb cross-section from BD0X, with D0 K - correlate D0 with of right (wrong) sign
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 8
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Fully reconstructed B events
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 9
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 10
Flavor physics at hadron colliders
Tracking• We need good Vertexing Particle Identification
Flavor program at LHC• LHC is also a b-factory
• Next generation of flavor program
• 40% Bu , 40% Bd, 10% Bs, 10% b-baryons
Bs is very hard at (Super-)B factories, but may be crucial for NP…
LHCb Experiment
It is not very easy to realize MFV in theoretical models
Tracking at ATLAS, CMS and LHCb
It is not very easy to realize MFV in theoretical models
Hadron ID
It is not very easy to realize MFV in theoretical models
Remarks on flavor physics
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 16
• It is not easy to reconcile the 2 points: - The SM is very successful in describing quark mixing - New physics TeV
Minimal Flavor Violation (MFV)
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 17
• In the Standard Model
• MFV Hypothesis
Yukawa coupling is unique source of flavor symmetry breaking also beyond the SM
It is not very easy to realize MFV in theoretical models
CKM Matrix
• At first sight the global CKM fit shows an excellent consistency.
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 18
CKM Matrix
• Closer inspection shows some tensions …
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 19
CKM Matrix • The sin2 & Br(B) tension: closer look
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 20
CKM Matrix
• LHCb will measure in trees and loops
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 21
Bs mixing
• Recent results from CDF & D0
- Bs J/ : 2.1 sigma -> 1.0 sigma
-> measures sin2s
- D0 observed a 3.2 sigma anomalous in like-sign dimuon charge asymmetry
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 22
2010/8/6 23Y. Gao, Prospects of flavor physics at the LHC
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 24
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 25
Bs mixing
• At LHCb, PID may help event selection and flavor tagging
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 26
Bs mixing
• Prospects
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 27
Bs,d →μ+μ−
• Very small in SM,
could be enhanced, e.g. in MSSM
• Current CDF (World’s best) limit
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 28
10
9
10)1.01.1()(Br
10)3.06.3()(Br
d
s
B
B
.).%95(101.9: Expected
.).%95(106.7)(Br
.).%95(103.3: Expected
.).%95(103.4)(Br
9
9
8
8
LC
LCB
LC
LCB
d
s
Bs,d →μ+μ− at LHCb
• Ways to enhance S/B
- Vertexing - Invariant mass - Muon ID
• Using control samples
• So far data consistent with MC background predictions
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 29
Bs →μ+μ− at LHCb
• LHCb roadmap
c.f. MC studies at 14 TeV
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 30
B K* +-
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 31
B K* +-
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 32
B K* +-
2010/8/6 Y. Gao, Prospects of flavor physics at the LHC 33
• Measurements seem favor • LHCb sensitivity:
0.1 fb-1 ~ B Factories
1.0 fb-1 ~ 4 sigma exclusion of SM (Assuming Belle central value)
Conclusion
• Flavor programs at LHC (and Super B Factories) will provide further precise measurements on CKM matrix elements, (very) rare decay rates which are sensitive to new physics beyond the Standard Model.
• Theory – Experiment interplay is essential to maximize the potential of these (expensive) programs.
• Complementary to experiments at high energy frontier, flavor physics will help us to explore features of the new physics, hopefully in near future.