Rare B decays at LHCb experiment

1. Rare B decays at LHCb experiment IakovenkoV.M. Institute for Nuclear Research, Kyiv, Ukraine on behalf of the LHCb collaboration NPAE'12, 3-7 September 2012

2. Outline • СКМ matrixand unitarity triangle • LHCb experiment • Rare leptonic B0(s) →µ+ µ-decay • Rare semileptonic B0→K*0µ+µ-decay • Radiative B0→K*γand B0s→φγdecays • Conclusions NPAE'12, 3-7 September 2012

3. СКМ matrixand unitarity triangle •  = 0.2254 ± 0.0006 • = 0.824 ± 0.013 ICHEP 12 •  = 0.142 ± 0.022 • = 0.363 ± 0.014 • α = 89.1 ± 3.0 • β = 22.28 ± 0.92 • γ = 68.5 ± 3.1 NPAE'12, 3-7 September 2012

4. 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 LHCb – the institute for beauty at LHC NPAE'12, 3-7 September 2012

5. The LHCb detector NPAE'12, 3-7 September 2012

6. Rare leptonic B0(s) →µ+ µ- decay (1) B0s →µ+ µ- is one the most promising channels for 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 →µ+ µ-)SM = (3.2 ± 0.2) x 10-9 B(B0→µ+ µ- )SM = (1.0 ± 0.1) x 10-10 ? JHEP 1010 (2010) 009, arXiv: 1005.5310 NPAE'12, 3-7 September 2012

7. Rare leptonic B0(s) →µ+ µ- decay (2) -SM signal -combinatorial background (from semileptonic B decays) -peaking background (B→hh´) -cross feed -uncertainty The most restrictive limits achieved by LHCb with 1.0 fb-1 of integrated luminosity: B(B0s →µ+ µ-) < 4.5 x 10-9 @ 95% CL B(B0→µ+ µ- ) < 1 x 10-9 @ 95% CL Phys. Rev. Lett. 108, 231801 (2012) NPAE'12, 3-7 September 2012

8. Rare semileptonic B0→K*0µ+µ- 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. CERN-LHCb-CONF-2012-008 NPAE'12, 3-7 September 2012

9. Rare semileptonic B0→K*0µ+µ-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. LHCB-PAPER-2012-011, arXiv: 1205.3422 NPAE'12, 3-7 September 2012

10. Radiative B0→K*γ and B0s→φγ 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) NP Theoretical predictions NPAE'12, 3-7 September 2012

11. Radiative B0→K*γ and B0s→φγdecays (2) LHCB-PAPER-2012-019, arXiv: 1209.0313 NPAE'12, 3-7 September 2012

12. Conclusions • Since it’s successful start LHCb has collected about 2 fb-1 integrated luminosity • The best limits in the measurements of B0(s)→µ+µ- up to now. Branching fraction of B0(s)→µ+µ- is compatible with SM signal prediction within 1 sigma and NP enhancements of B(B0s→µ+µ- ) are constrained to be much smaller than the SM prediction. • Most precise measurement of branching fraction for B0s→φγ • Angular distributions of B0→K*0µ+µ- 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 data NPAE'12, 3-7 September 2012