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 2010/8/61Y. 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 - B s mixing - Rare decays Conclusion 2010/8/6Y. Gao, Prospects of flavor physics at the LHC2

LHC is running… ~400 nb -1 /experiment delivered to ATLAS, CMS, LHCb Date collected with high efficiencies (> 90%) Much more underway… 2010/8/6Y. Gao, Prospects of flavor physics at the LHC3 LHCb operation

Quarkonia production Signals seen from data ! 2010/8/6Y. Gao, Prospects of flavor physics at the LHC4

Quarkonia production J/  in central region J/  in forward region 2010/8/6Y. Gao, Prospects of flavor physics at the LHC5 CMS preliminary : (4≤p T ≤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 : (p T ≤10GeV/c and 2.5<y <4) σ(pp→J/ψ + X) = (7.65 ± 0.19(stat) ± 1.10(syst) )  b Data favor neither color singlet nor color octet model.

Quarkonia production  1s, 2s and 3s  →μ+μ /8/6Y. Gao, Prospects of flavor physics at the LHC6 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 2010/8/6Y. Gao, Prospects of flavor physics at the LHC7 CMS preliminary : (4≤p T ≤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 : (p T ≤10GeV/c and 2.5<y <4) σ(pp→ bX→ J/ψX’) = (0.81 ± 0.06(stat) ± 0.13(syst) )  b - - -

bb cross-section bb cross-section from B  D 0  X, with D 0  K  - correlate D 0 with  of right (wrong) sign 2010/8/6Y. Gao, Prospects of flavor physics at the LHC8 - -

Fully reconstructed B events 2010/8/6Y. Gao, Prospects of flavor physics at the LHC9

2010/8/6Y. Gao, Prospects of flavor physics at the LHC10

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% B u, 40% B d, 10% B s, 10% b-baryons B s 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 2010/8/6Y. Gao, Prospects of flavor physics at the LHC16 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) 2010/8/6Y. Gao, Prospects of flavor physics at the LHC17 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. 2010/8/6Y. Gao, Prospects of flavor physics at the LHC18

CKM Matrix Closer inspection shows some tensions … 2010/8/6Y. Gao, Prospects of flavor physics at the LHC19

CKM Matrix The sin2  & Br(B  ) tension: closer look 2010/8/6Y. Gao, Prospects of flavor physics at the LHC20

CKM Matrix LHCb will measure  in trees and loops 2010/8/6Y. Gao, Prospects of flavor physics at the LHC21

B s mixing Recent results from CDF & D0 - B s  J/   : 2.1 sigma -> 1.0 sigma -> measures sin2  s - D0 observed a 3.2 sigma anomalous in like-sign dimuon charge asymmetry 2010/8/6Y. Gao, Prospects of flavor physics at the LHC22

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B s mixing At LHCb, PID may help event selection and flavor tagging 2010/8/6Y. Gao, Prospects of flavor physics at the LHC26

B s mixing Prospects 2010/8/6Y. Gao, Prospects of flavor physics at the LHC27

B s,d →μ + μ − Very small in SM, could be enhanced, e.g. in MSSM Current CDF (World’s best) limit 2010/8/6Y. Gao, Prospects of flavor physics at the LHC28

B s,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 2010/8/6Y. Gao, Prospects of flavor physics at the LHC29

B s →μ + μ − at LHCb LHCb roadmap c.f. MC studies at 14 TeV 2010/8/6Y. Gao, Prospects of flavor physics at the LHC30

B  K *  +  /8/6Y. Gao, Prospects of flavor physics at the LHC31

B  K *  +  /8/6Y. Gao, Prospects of flavor physics at the LHC32

B  K *  +  /8/6Y. Gao, Prospects of flavor physics at the LHC33 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.