Prospects of Search for New Physics

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


In CP-violation


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


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 Standard strategy to search for New Physics


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


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


b q u, c, t u, c, t q b W+ W− V*ib Viq Viq V*ib trees d-/s- penguins d-/s- boxes Compare experimental observables measured in different topologies: Complementary Strategy


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 |VtsVtb*| and UT angles: ,  and 


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/) For |VtsVtb*| (at the moment not theoretically clean): Proposed set of observables Theoretical input: improved precision of lattice calculations for B×fB and B,,K* formfactors Experimental input: precision measurement of BR(BK*, )


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)) andlt; 30° (d-penguin) - (2(NP)) ~8° (2.6 hint) (s-penguin) - ((NP)) not measured yet (s-penguin) PS (NP) =  (NP)


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) LHCb (see M.John talk)


In Rare Decays


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


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


Radiative Penguin Decays 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 or parity-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 b   (L) + (ms/mb)  (R)


Polarized b decays: b  (1115) (1115)  p violates pariry Assuming b polarization andgt; 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. 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 )


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 !!!) Promising channels for LHCb: Expected yield per 2 fb-1 BR(B+  K+-+) ~ 2.5  10-5 rich pattern of resonances ~60k BR(B+  K+) ~ 3  10-6 highly distinctive final state ~ 7k Sensitivity to photon helicity measurement is being studied 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

Bd → K*mm decay: 

Bd → K*mm decay Bd m m g K* In SM, the decay is a b → s penguin diagram But NP diagrams could also contribute at the same level d d For 2 fb-1 LHCb expects 7200±2100 signal events .(Uncertainty mostly due to BR) with a B/S andlt; 0.5 Branching ratio:(1.22+0.38 -0.32) 10-6 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




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


LHCb prospects: 

LHCb prospects

Rare decays: Bs → mm(for LHCb prospects see M. John talk): 

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): andlt; 7 x 10 -8 Expected final limit at 95% CL (8 fb-1): andlt; 2 x 10 -8 Sensitive to New Physics through loops Could be strongly enhanced by SUSY.

Example: constrained minimal SSM: CMSSM: 

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 andlt; m1/2 (gaugino mass) andlt; 650 GeV 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: 10-7 10-8 10-9


LHC Prospects


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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