Rare B decays at LHCb experiment

*Rare B decays at LHCb experiment

Iakovenko V.M.Institute for Nuclear Research, Kyiv, Ukraineon behalf of the LHCb collaborationNPAE'12, 3-7 September 2012

NPAE'12, 3-7 September 2012

*Outline matrix and unitarity triangle LHCb experimentRare leptonic B0(s) + - decayRare semileptonic B0K*0+- decayRadiative B0K* and B0s decaysConclusionsNPAE'12, 3-7 September 2012


* matrix and unitarity triangle = 0.2254 0.0006= 0.824 0.013 ICHEP 12 = 0.142 0.022= 0.363 0.014 = 89.1 3.0 = 22.28 0.92 = 68.5 3.1NPAE'12, 3-7 September 2012


* LHCb the institute for beauty at LHC

Dedicated experiment to study CP violation and other rare phenomena in B meson decays; Precision measurement of CKM parameters; Test of SM predictions / search for NP The LHCb detector is a single-arm dipole spectrometer which uses sharply peaked forward-backward bb production cross-section

Expect ~1012 b-hadrons per year

All b-species are produced: Bu ( ~40%), Bd (~40%), Bs (~10%), Bc (~0.1%)

Experimental attributes of LHCb include efficient tracking, particle identification and excellent vertexing



* The LHCb detectorNPAE'12, 3-7 September 2012


*Rare leptonic B0(s) + - decay (1)B0s + - is one the most promising channelsfor detecting signals of new physics at LHCb and constrain SUSY models. Evidences of NP may occur via transitions induced by flavor changing neutral currents.

The branching ratio is well predicted within the Standard Model:

B(B0s + -)SM = (3.2 0.2) x 10-9 B(B0 + - )SM = (1.0 0.1) x 10-10

NPAE'12, 3-7 September 2012 ?JHEP 1010 (2010) 009, arXiv: 1005.5310


*Rare leptonic B0(s) + - decay (2)The most restrictive limits achieved by LHCb with 1.0 fb-1 of integrated luminosity: B(B0s + -) < 4.5 x 10-9 @ 95% CL B(B0 + - ) < 1 x 10-9 @ 95% CLPhys. Rev. Lett. 108, 231801 (2012)

NPAE'12, 3-7 September 2012 -SM signal-combinatorial background (from semileptonic B decays)-peaking background (Bhh)-cross feed -uncertainty


*Rare semileptonic B0K*0+- decay (1)Several angular variables can be fitted to search for new physics in a clean theoretical environment, like forward-backward asymmetry of the muons, AFB, and the fraction of longitudinal polarization, FL, as functions of the dimuon invariant mass squared, q2.

NPAE'12, 3-7 September 2012 CERN-LHCb-CONF-2012-008


*Rare semileptonic B0K*0+- decay (2)LHCb results of this channel are the most precise and compatible with SM predictions.

The zero crossing point for AFB at q20 = 4.9+1.1-1.3 GeV2/c4, which is in agreement with SM prediction which range from 4.0 - 4.3 GeV2/c4.

NPAE'12, 3-7 September 2012 LHCB-PAPER-2012-011, arXiv: 1205.3422


*Radiative B0K* and B0s decays (1)

Radiative penguin decays also provide a good tool to search physics beyond SM. Branching ratio is predicted with Operator Product Expansion (OPE) separation of the B meson decay amplitude:long-distance (operator matrix elements)short distance (Wilson coefficients)

NPAE'12, 3-7 September 2012 Theoretical predictions

NP


*NPAE'12, 3-7 September 2012 Radiative B0K* and B0s decays (2)LHCB-PAPER-2012-019, arXiv: 1209.0313


*ConclusionsSince its successful start LHCb has collected about 2 fb-1 integrated luminosity The best limits in the measurements of B0(s)+- up to now. Branching fraction of B0(s)+- is compatible with SM signal prediction within 1 sigma and NP enhancements of B(B0s+- ) are constrained to be much smaller than the SM prediction. Most precise measurement of branching fraction for B0s Angular distributions of B0K*0+- are in consistency with SM. Waiting for better statistic.By the end of 2012 it is expected to collect about 3.2 fb-1 integrated luminosity

All results obtained with 1 fb-1 of dataNPAE'12, 3-7 September 2012


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Rare B decays at LHCb experiment

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