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Prospects of search for New Physics in B decays at LHC

Andrey Golutvin ITEP / Moscow. Prospects of search for New Physics in B decays at LHC. In CP - violation In rare decays. In CP-violation. Mean values of angles and sides of UT are entirely consistent with SM predictions. Inputs:. Accuracy of angles is limited by experiment:

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Prospects of search for New Physics in B decays at LHC

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  1. Andrey Golutvin ITEP / Moscow Prospects of search for New Physics in B decays at LHC • In CP - violation • In rare decays Andrey Golutvin Moriond 2007

  2. In CP-violation

  3. Mean values of angles and sides of UT are entirely consistent with SM predictions Inputs: Accuracy of angles is limited by experiment: • = ±13° • b = ± 1.5° • = ± 25° • Accuracy of sides is limited by theory: • Extraction of |Vub| • Lattice calculation of 3

  4. Standard strategy to search for New Physics Define the apex of UT using at least 2 independent quantities out of 2 sides: and 3 angles: ,  and  Extract quantities Rb and  from the tree-mediated processes, that are expected to be unaffected by NP, and compare computed values for with direct measurements in the processes involving loop graphs. Interpret the difference as a signal of NP

  5. At present the sensitivity of standard approach is limited due to: - Theoretical uncertainties in sides - Experimental uncertainties in  and  angles - Geometry of UT (UT is almost rectangular) Comparison of precisely measured  with  is not meaningful due to error propagation: 3° window in  corresponds to (245)° window in  5

  6. Precision comparison of the angle  and side Rt is very meaningful !!! ~5% theoretical precision in Rt is adequate to a few degree experimental precision in the angle  which should be achievable after 1 year of LHC running Precision measurement of  will effectively constrain Rt and thus calibrate the lattice calculation of the parameter

  7. W– q1 b q b u, c, t q2 W− d, s mbγL+mqγR W − W − d (s) d (s) b u,c,t b u, c, t l+ q g Z, γ l− q Complementary Strategy trees Compare experimental observables measured in different topologies: d-/s- penguins d-/s- boxes V*ib Viq q u, c, t b W− W+ u, c, t q b Viq V*ib

  8. |VtsVtb*| and UT angles: ,  and  • trees vs box loops vs penguin loops • In trees: • (tree) is measured in B J/Ks • (tree) =  - (tree) - (tree) (tree) is measured in B J/ • Precision measurements of angles in tree topologies should be possible. Eventually LHCb will measure , , and  with () ~ 0.5°, () ~ few° and • () ~ 1° precision respectively Theoretical uncertainty in Vub extraction

  9. Proposed set of observables For |VtsVtb*| (at the moment not theoretically clean): Theoretical input: improved precision of lattice calculations for B×fB and B,,K* formfactors Experimental input: precision measurement of BR(BK*, ) For the angles: (theoretically clean) Measure (peng) in B,, (peng) in BKs (peng) in Bs New heavy particles, which may contribute to d- and s- penguins, would lead to some phase shifts in all three angles: (NP) = (peng) - (tree) (NP) = (BKs) - (BJ/Ks) (NP) = (B) - (BJ/)

  10. Contribution of NP to processes mediated by loops (present status) To boxes: -  vs Rb is limited by theory (~10% precision in Rb) (d-box) -  poorly measured at the moment (s-box) To penguins: -((NP)) < 30° (d-penguin) - (2(NP)) ~8° (2.6 hint) (s-penguin) - ((NP)) not measured yet (s-penguin) PS (NP) =  (NP)

  11. LHCb (see M.John talk) ATLAS: similar to LHCb sensitivity in  with 30 /fb s(s) ~ 0.08 (10/fb, Dms=20/ps, 90k J/ evts) CMS:s(s) ~ 0.07 (10/fb, on J/ evts, no tagging)

  12. In Rare Decays

  13. Radiative penguins • Electroweak penguins • Very rare decays Bs,d  , e Experimental challenge: keep backgrounds under control

  14. Exclusive radiative penguins LHCb control channel: Bd K* ~75k signal events per 2fb-1 13

  15. Radiative Penguin Decays b   (L) + (ms/mb)  (R) Measurement of the photon helicity is very sensitive test of SM Methods: -mixing induced CP asymmetries in Bs  , BKs 0 - b   : asymmetries in the final states angular distributions are sensitive to the photon and b polarizations. - Photon helicity can be measured directly using converted photons in BK* decay orparity-odd triple correlation (P(),[ P(h1)  P(h2)]) between photon and 2 out of 3 final state hadrons. Good examples are B K and B K decays

  16. Mixing induced CP asymmetries - B  BKs0  (B-factories) S = - (2+O(s))sin(2)ms/mb + (possible contribution from bsg) = - 0.022 ± 0.015 P.Ball and R.Zwicky hep-ph/0609037 Present accuracy: S = - 0.21 ± 0.40 (BaBar : 232M BB) S = - 0.10 ± 0.31 (BELLE: 535M BB) - Bs    ( LHCb annual yield ~11 k , B/S ~0.6 ) Polarized b decays: b  (1115) (1115)  p violates pariry Assuming b polarization > 20% LHCb can measure (R) component down to 20% (in 1 years of data taking). Limitation - low annual yield (~675 events)  requires efficient performance of tracking system.

  17. Measuring the photon polarization in B  h1h2h3 decays The measurement of the photon helicity requires the knowledge of the spin direction of the s-quark emitted from the penguin loop. Use the correlation between s-spin and angular momentum of the hadronic system (needs partial-wave analysis !!!) M.Gronau,Y.Grossman,D.Pirjol,A.Ryd PRL 88, 5, 2002 D.Atwood,T.Gershon,M.Hazumi,A.Soni hep-ph/0701021 v 1 V. Shevchenko paper in preparation Promising channels for LHCb: Expected yield per 2 fb-1 BR(B+ K+-+) ~ 2.5  10-5rich pattern of resonances~60k BR(B+ K+) ~ 3  10-6 highly distinctive final state ~ 7k Sensitivity to photon helicity measurement is being studied

  18. b s Bd→ K*mmdecay In SM, the decay is a b → s penguin diagram But NP diagrams could also contribute at the same level d d Bd K* m g m • In addition to the virtual photon, • there will be Z0 contributions • Which will add some calculable • right handed contributions. • But these could be added to by New Physics • Resulting in modified angular distributions Branching ratio:(1.22+0.38-0.32) 10-6 For 2 fb-1 LHCb expects 7200±2100 signal events .(Uncertainty mostly due to BR) with a B/S < 0.5

  19. 18

  20. Kreuger, Matias hep-ph/0502060 Prospects for Forward-Backward asymmetry measurements (see M. John talk)

  21. LHCb prospects

  22. ? ? MSSM Rare decays: Bs→mm(for LHCb prospects see M. John talk) • Very small branching ratio in SM: (3.4 ± 0.5) x 10-9 • Present limit from Tevatron at 95% CL(1 fb-1): < 7 x 10 -8 • Expected final limit at 95% CL (8 fb-1): < 2 x 10 -8 • Sensitive to New Physics through loops • Could be strongly enhanced by SUSY.

  23. Example: constrained minimal SSM: CMSSM Anomalous magnetic moment of muon: Measured at BNL, disagrees with SM at 2.7. am = (25.2 ±9.2) 10-10. To explain it with CMSSM: for different A0 and tan: 250 < m1/2 (gaugino mass) < 650 GeV 10-7 10-8 10-9 CMSSM with this same range of gaugino mass predicts BR (Bs → m+m-) could be ~ a few 10-9 to 10-7 much higher than SM:

  24. LHC Prospects LHCb Sensitivity (signal+bkg is observed) Limit at 90% C.L. (only bkg is observed) BR (x10-9) BR (x10-9) 5 Expected CDF+D0 Limit SM prediction 3 Uncertainty in bkg prediction SM prediction Integrated Luminosity (fb-1) Integrated Luminosity (fb-1)

  25. Important measurements to test SM and Search for NP • In CP-violation: •  vs Rb and  vs Rt (Input from theory !) •  : if non-zero  NP in boxes • (NP), (NP) and (NP): if non-zero  NP in penguins • In rare decays: • Photon helicity in exclusive radiative penguins • Measurement of FBA, zero point, transversity amplitudes in Bsll • exclusive decays (K*, , …) • Measurement of BR(B s,d  ) down to SM predictions • Search for lepton flavor violation

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