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Andrey Golutvin ITEP & CERN Promising measurements for the test of SM and search for New Physics - In CP - violation - In rare decays LHCb upgrade workshop, Edinburgh, 2007 1 In CP-violation 2 Mean values of angles and sides of UT are entirely consistent with SM predictions Inputs: Vub Vcb Δmd Δms B → τν εK sin2β α γ Accuracy of sides is limited by theory: - Extraction of |Vub| - Lattice calculation of Accuracy of angles is limited by experiment: α= ± 13° 33 β = ± 1.5° γ = ± 25° 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: α, β and γ Extract quantities Rb and γ 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 4 At present the sensitivity of standard approach is limited due to: - Theoretical uncertainties in sides - Experimental uncertainties in α and γ angles - Geometry of UT (UT is almost rectangular) Comparison of precisely measured β with γ is not meaningful due to error propagation: 3° window in β corresponds to (24±5)° window in γ 5 5 Precision comparison of the angle γ and side Rt is very meaningful !!! However in many NP scenarios, in particular with MFV, short-distance contributions are cancelled out in the ratio of ΔMd/ΔMs. So the length of the Rt side may happen to be not sensitive to NP Precision measurement of γ will effectively constrain Rt and thus calibrate the lattice calculation of the parameter 6 Complementary Strategy trees Compare experimental observables measured in different topologies: q1 b q2 W− Bq d, s d-/s- penguins W– b W− W− q b u, c, t d (s) b u, c, t mγ b L +m l+ Z, γ qγ R u,c,t d (s) q g q l− d-/s- boxes V*ib q u, c, t b Bq Viq W− W+ u, c, t q Viq b V*ib Bq 7 |VtsVtb*| and UT angles: α, β and χ trees vs box loops vs penguin loops In trees: β(tree) is measured in BÆ J/ψKs α(tree) = π - β(tree) - γ(tree) χ(tree) is measured in BÆ J/ψφ Theoretical uncertainty in Vub extraction Precision measurements of angles in tree topologies should be possible. Eventually LHCb will measure β, γ, and χ with σ(β) ~ 0.5°, σ(γ) ~ few° and σ(χ) ~ 1° precision respectively 8 Proposed set of observables For |VtsVtb*| (at the moment not theoretically clean): Theoretical input: improved precision of lattice calculations for BØfB and BÆπ,ρ,K* formfactors Experimental input: precision measurement of BR(BÆK*γ, ργ) For the angles: (theoretically clean) Measure α(peng) in BÆρρ,ρπ,ππ β(peng) in BÆφKs χ(peng) in BsÆφφ New heavy particles, which may contribute to d- and s- penguins, would lead to some phase shifts in all three angles: δα(NP) = α(peng) - α(tree) δβ(NP) = β(BÆφKs) - β(BÆJ/ψKs) δχ(NP) = χ(BÆφφ) - χ(BÆJ/ψφ) 9 Contribution of NP to processes mediated by loops Present status: To boxes: - β vs Rb is limited by theory (~10% precision in Rb) (d-box) - χ not measured yet (s-box) To penguins: - σ(δα(NP)) ~ 30° - σ(δ2β(NP)) ~8° (2.6σ hint) - σ(δχ(NP)) not measured yet (d-penguin) (s-penguin) (s-penguin) ps δβ(NP) = δχ (NP) 10 In Rare Decays 11 - Radiative penguins - Electroweak penguins - Very rare decays Bs,d Æ μμ, eμ Experimental challenge: keep backgrounds under control 12 Exclusive radiative penguins LHCb control channel: Bd Æ K*γ ~75k signal events per 2fb-1 13 13 Radiative Penguin Decays γR m qγ R + γL W– mb W+ q b +m b m qγ L q b u, c, t u, c, t Measurement of the photon polarization is very sensitive test of SM Methods: - mixing induced CP asymmetries in Bs Æ φγ , BÆKs π0γ - Λb Æ Λγ : asymmetries in the final states angular distributions are sensitive to the photon and Λb polarizations. - Photon helicity can be measured directly using converted photons in BÆK*γ decay 3 or parity-odd triple correlation (P(γ),[ P(h1) × P(h2)]) between photon and 2 out of 14 final state hadrons. Good examples are BÆ φKγ and BÆ Kππγ decays Mixing induced CP asymmetries - B Æ BÆKsπ0 γ (B-factories) S = - (2+O(αs))sin(2β)ms/mb + (possible contribution from bÆsγg) = - 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 Æ φ γ ( LHCb annual yield ~11 k , B/S ~0.6 ) Polarized Λb decays: Λb Æ Λ(1115)γ Λ(1115) Æ pπ violates pariry Assuming Λb polarization > 20% LHCb can measure γ(R) component down to 20% (in 1 years of data taking). Limitation - low annual yield (~675 events) Æ requires efficient performance of tracking system. 15 Measuring the photon polarization in B Æ h1h2h3 γ 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 !!!) The average value of the triple product [ P(γ) × [P(h1) × P(h2)]] has opposite signs for left – and right-handed photons 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 Promising channels for LHCb: Expected per 2 fb-1 BR(B+ Æ K+π-π+γ) ~ 2.5 × 10-5 rich pattern of resonances highly distinctive final state BR(B+ Æ K+φγ) ~ 3 × 10-6 Sensitivity to photon polarization measurement to be studied ~40k ~10k 16 Exclusive bÆsμμ decaus Bd Æ K*0μ+μB+ Æ K+μ+μBs Æ φ μ+μ- Λb Æ Λ μ+μ- Described by a combination of γ - and Z – penguins and box diagrams Æ Sensitive to New Physics: SUSY, graviton exchanges, extra dimensions … 17 17 18 18 Kreuger, Matias hep-ph/0502060 19 20 20 21 B s,d Æ μ+μBs Æ μ+μ- measurement seems to be possible (see talk by O. Schneider) Bd decay has a SM BR an order of magnitude lower ; not reachable with present LHCb configuration. Can probe NP models with different contribution to s- and d-loops 22 LHCb Prospects LHCb Sensitivity Limit at 90% C.L. (signal+bkg is observed) 10 10 9 8 BR (x10-9) BR (x10-9) (only bkg is observed) 2 7 6 5 5σ Expected CDF+D0 Limit 4 SM prediction 3 10 3σ 2 Uncertainty in bkg prediction SM prediction 1 0 0.1 0.2 0.3 0.4 0.5 Integrated Luminosity (fb-1) 1 0 1 2 3 4 5 6 7 8 9 10 Integrated Luminosity (fb-1) Background is assumed to be dominated by combinations of bÆμ-X bÆμ+X 23 events. Important measurements to test SM and Search for NP In CP-violation: -β vs Rb and γ vs Rt (Input from theory !) -χ : if non-zero Æ NP in boxes -δα(NP), δβ(NP) and δχ(NP): if non-zero Æ NP in penguins In rare decays: -Photon polarization in exclusive radiative penguins - Measurement of FBA, zero point, transversity amplitudes in BÆsll exclusive decays (K*μμ, φμμ, …) - Measurement of BR(B s,d Æ μμ) down to SM predictions - Search for lepton flavor violation 24