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M. Adinolfi - University of Bristol1/19 Valencia, 15 December 2008 High precision probes for new physics through CP-violating measurements at LHCb M. Adinolfi University of Bristol On behalf of the LHCb collaboration
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M. Adinolfi - University of Bristol2/19 Valencia, 15 December 2008 Introduction LHCb is a 2 nd generation precision experiment following Tevatron and the B-factories b -> c transitions: extensively studied and in good agreement with SM b -> s transitions: limited knowledge, room for NP effects Precision measurements available for CKM parameters, allowing strong constraints on SM, but still poorly measured. Collection of large sample of b (c) hadrons at LHC allows extensive study in a wide set of channels. Rare decays - see Hugo Ruiz presentation Early LHCb results - see Abraham Gallas presentation B s mixing with trees with loops Mixing and CPV in charm
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M. Adinolfi - University of Bristol3/19 Valencia, 15 December 2008 LHCb in a nutshell Real beam gas event High statistics: L ~ 2 x 10 32 cm -2 s-1 bb ~ 500 b at 14 TeV ~ 10 12 bb year (2 fb -1 ) B ±, B 0, B s, B c, b … Tracking: Mass resolution: B(D) ~ 15(7) MeV B vertex resolution: z ~ 200 m Proper time resolution: ~ 40 fs Particle identification: /K separation over 2 GeV < p < 100 GeV Trigger: First level (L0) High p T hadron trigger
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M. Adinolfi - University of Bristol4/19 Valencia, 15 December 2008 B s phase s B s -> J/Ψ dominated by tree NP can enter through mixing B s -> dominated by a penguin NP can enter through mixing and/or penguin In presence of NP the mixing phase Is modified and can probe NP in the mixing ( M NP ) and/or the penguin ( D NP ). Tevatron results: D0 s = 0.57 + 0.24 -0.30 with 2.8 fb -1 CDF s = [0.32,2.82] @ 68%CL with 1.35 fb -1 The observable is s = SM + NP In SM S (B s -> J/Ψ ) = -2 s = -0.0368 ± 0.0017 s (B s -> ) = 0
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M. Adinolfi - University of Bristol5/19 Valencia, 15 December 2008 B s phase s (2) s can be extracted from CP time-dependent asymmetry in decay rates : with n f = ±1 CP eigenstate Would like to use pure CP eigenstates such as B s J/Ψ η, B s J/Ψ η’, B s η c Φ, B d D s + D s - But low yield and high background B s -> J/Ψ has a nice signature and large yield small background but is a mixture of CP = +1 and CP = -1 states requires an angular analysis to disentangle the two states Combined D0 and CDF 2.2 from SM (ICHEP08)
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M. Adinolfi - University of Bristol6/19 Valencia, 15 December 2008 B s phase s (3) Similar analysis yields 3.4k events (2 fb -1 ) with an expected sensitivity on s B s -> ( s ) ~ 0.125 115k 0.03
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M. Adinolfi - University of Bristol7/19 Valencia, 15 December 2008 Angle plays a unique role in flavour physics Can be measured through tree diagrams and those involving loops Trees Benchmark for SM Time integrated (GLW, ADS, Dalitz/GGSZ) and/or time dependent strategies Loops Sensitive to NP Measured at B factories A full test of SM and unitarity requires: ~ a few degrees measurement in B ±, B 0 and B s = 77° + 30° - 32°
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M. Adinolfi - University of Bristol8/19 Valencia, 15 December 2008 GLW method: f D is a CP eigenstate common to D 0 and D 0 : f D = K + K -, + -,… Measure: B → D 0 K, B → D 0 K, B → D 1 K Large event rate; small interference Measurement r B difficult from trees: B -> DK B–B– D0K–D0K– D0K–D0K– fDK–fDK– b c favoured b u suppressed Decay time independent analysis Cabibbo supp. Cabibbo allowed. Interfere decays b c with b u to final states common to D 0 and D 0 color suppression ADS method: Use common flavour state f D =(K + – ) Note: decay D 0 → K + – is double Cabibbo suppressed Lower event rate; large interference 8
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M. Adinolfi - University of Bristol9/19 Valencia, 15 December 2008 from trees: B ± -> D(hh) K ± ChannelYield (2 fb -1 )B/S B + → D(K ) K + Favoured 28 k0.6 B + → D(K ) K + Suppressed 6501.2 B + → D(KK) K + Favoured3k1.2 B + → D( ) K + Suppressed 1k3.6 ADS and GLW 6 rates, 5 unknown parameters Assuming: = 60° r B = 0.10 B = 130° (PDG) r D = 0.0616 (PDG) D centered at 158° (ADS requires -180 shift w.r.t. published D from CLEO-c) = 10.8° – 12.7° depending on D
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M. Adinolfi - University of Bristol10/19 Valencia, 15 December 2008 from trees: Combining all ADS - GLW = 7° – 9.5°
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M. Adinolfi - University of Bristol11/19 Valencia, 15 December 2008 from trees: B ± -> D(K s + - ) K ± K s + - Dalitz plot contain a CP-violating contribution from the decay path sensitive to Two different method of analysis Unbinned fit based on amplitude model Model independent binned fit using ψ(3770) results on D decays. Background suppressed with RICH and momentum cut Yield ~ 5k per year Statistical uncertainty = 9.8° Amplitude model = 12.8° Binned fit Amplitude model also affected by uncertainty due to the model. Latest BaBar analysis estimate 7° Binned fit affected by finite statistics in Ψ sample, estimated 2°.
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M. Adinolfi - University of Bristol12/19 Valencia, 15 December 2008 from trees: B s -> D s K Interference between tree decays via mixing Insensitive to NP Measures + s ( s measured from B s ->J/Ψ ) Include B s ->D s to determine m s and tagging dilution Simultaneous fit to both decays Assuming = 60° and m s = 17.5 ps -1 B s → D s - K + ChannelYield (2 fb -1 )B/S B s → D s K6.2 k0.7 B s → D s 140 k0.2 = 10.3°
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M. Adinolfi - University of Bristol13/19 Valencia, 15 December 2008 from loops: B -> hh B d/s /K B d/s Interference between tree and penguin diagrams Measure time-dependent CP asymmetries for B 0 and B s Assume U-spin flavour symmetry (d s) d = d’ and = ’ Take d from B d J/ K s and s from B S J/ solve for 4 observables, 3 unknowns
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M. Adinolfi - University of Bristol14/19 Valencia, 15 December 2008 from loops: B -> hh (2) Bs K+K- BG 2 fb -1 ms=20 Time 14 ChannelYield (2 fb -1 )B/S B s → KK36 k< 0.06 B 0 → 36 k0.5 WITH RICH PID NO PID
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M. Adinolfi - University of Bristol15/19 Valencia, 15 December 2008 Different ways to measure B modeD modeMethodParameter Bs→DsKBs→DsK KK tagged, A CP (t) -s-s B + → D K + K ,KK/ counting, ADS+GLW B + → D K + K s Dalitz, GGSZ B + → D K + KK 4 body Dalitz B 0 → D K *0 K ,KK, counting, ADS+GLW B → ,KK -tagged, A CP (t) / d / s 2fb -1 9°-12° 11º-13º 10º-13º 18º 5º-12° 4º B ° (°) 04590135180 Combined B + /B 0 (ADS+GLW) 4.6°7.6°6.3°7.1°4.6° + model independent Dalitz4.1°5.1°4.8°5.1°3.9° 2fb -1 Combining with time dependent measurements a global sensitivity with tree decays only in 2 fb -1 ~ 4°
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M. Adinolfi - University of Bristol16/19 Valencia, 15 December 2008 Charm physics – Trigger and yields Dedicated D* -> D 0 (hh) trigger stream Loose cuts on hadrons pt, IP, D0 mass, D* - D0 mass difference RICH information not used in the trigger Present selection favours D* coming from B decays Estimated yields for secondary D 0 for 2 fb -1 D 0 -> K - + (right sign) 12.4 M D 0 -> K + - (wrong sign) 46.5 K D 0 -> K + K - 1.6 M D 0 -> + - 0.5 M Similar amounts expected for prompt production.
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M. Adinolfi - University of Bristol17/19 Valencia, 15 December 2008 Charm physics - D 0 mixing Sensitive to NP in the box diagram loop Recently observed at BaBar Belle and CDF x = 0.89± % 0.26 0.27 y = 0.75± % 0.17 0.18 Time-dependent D0 mixing with wrong-sign D 0 K + – decays stat (x’ 2 ) ~0.14 x10 –3, stat (y’) ~2 x10 –3 with 2 fb –1 D unambiguously tagged at production by the sign of the slow in the D* decay
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M. Adinolfi - University of Bristol18/19 Valencia, 15 December 2008 Charm physics – Direct CP violation Direct CP violation can be measured in D 0 KK lifetime asymmetry ACP<10 -3 in SM, up to 1% with New Physics current HFAG (average Belle, BaBar, CDF): ACP = -0.16 ± 0.23 Expect stat (ACP) ~ 0.001 with 2 fb –1
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M. Adinolfi - University of Bristol19/19 Valencia, 15 December 2008 Conclusions LHCb is a heavy flavour precision experiment searching for New Physics in CP Violation and rare decays CP Violation: 2 fb -1 (1 year) from trees: 4 o from loops: 10 o B s mixing phase: 0.023
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