in rappresentanza di LHCb Italia Vincenzo Vagnoni in rappresentanza di LHCb Italia Riunione CSN1 Napoli, 22 Settembre 2005

Current status of ms and s Despite the “heroic” efforts at LEP, SLD and CDF Run-I (now also CDF/D0 Run-II), ms is still unmeasured although there is an interesting feature in the amplitude plot at ~18 ps-1 Differently, first measurements of s from BsJ/ exist CDF: D0: Theory Constraint from semileptonic lifetime Direct measurement Combined result: ~2 above expectations disfavours low ms value! ms > 14.5 ps-1 at 95% CL Sensitivity at 18.5 ps-1

Unitarity Triangle Fits Collaboration M. Bona, M. Ciuchini, E. Franco, V. Lubicz, G. Martinelli, F. Parodi, M. Pierini, P. Roudeau, C. Schiavi, L. Silvestrini, A. Stocchi, V. Vagnoni

Prediction of ms from Unitarity Triangle fits p.d.f. for ms in SM without using its current experimental limit ms > 31 ps-1 @ 3 σ > 38 ps-1 @ 5 σ “Compatibility plot” for an hypotetical future measurement ms = 22.2 ± 3.1 ps-1

Relevance of LQCD for exploiting precise md,s measurements in Unitarity Triangle fits md,s enter the UT fits through the constraints It is crucial to improve the precision on the Lattice quantities (now at 10-15%) in order to fully exploit the current and future measurements of md and ms where the long distance hadronic quantities are calculated in the framework of LQCD:

New Physics model independent parametrization in |F|=2 transitions The mixing processes being characterized by a single amplitude, they can be parametrized in a general way by means of two parameters HSMeff includes only SM box diagrams while Hfulleff includes New Physics contributions as well See e.g. M. Bona et al., hep-ph/0509219 and refs. therein Four “independent” observables (C=1, =0 in SM) CBd, Bd, CBs, Bs For the neutral kaon mixing case, it is convenient to introduce only one parameter mK is not considered since the long distance effects are not well controlled

Exercise already done for the K0 and B0 mixing CK = 0.95 ± 0.22 [0.64, 1.45] @95% Macroscopic effects from New Physics in K0 and B0 mixing are absent Exercise already done for the K0 and B0 mixing Still 50% room for New Physics in md amplitude But the New Physics mixing phase must be close to zero CBd = 1.21 ± 0.46 [0.45, 2.50] @95% fBd = -4.5 ± 2.6 [-9.4, 0.9] @95%

What to say then? New Physics in the bd sector starts to be quite constrained and most probably will not come as an alternative to the CKM picture, but rather as a «correction» Basically two scenarios Minimal Flavour Violation: the only source of flavour violation is in the SM Yukawa couplings (implies =0) New Physics couplings between third and second families (bs sector) are stronger with respect to the bd ones Flavour physics needs to improve existing measurements in the Bd sector and perform precise measurement in the Bs sector: Physics case for SuperB and LHCb

bb production and detection at LHCb all b-hadron species are produced: ~40% ~10% p Parton 1 x1 Parton 2 x2 p 

Partial readout: Vertex Locator Trigger System 1 MHz Calorimeter Muon system Pile-up system Hard. Level-0 pT of m, e, h, g 40 MHz 40 kHz Soft. Level-1 Impact parameter Rough pT ~ 20% Partial readout: Vertex Locator Trigger Tracker Level 0 objects 2 kHz output Soft. HLT Final state reconstruction Full detector information 1 MHz readout is the new baseline solution as decided these days (see Umberto’s)

Trigger output bandwidths (2 kHz total) Original baseline stream 200 Hz: exclusive trigger Exclusive reconstruction of B decays “Real life” streams 600 Hz: di-muon trigger No bias from impact parameter cuts, this stream is particularly relevant to study the proper time resolution from data itself (very important for ms) Reconstruction of exclusive b-hadron  J/ X decay, for spectroscopy and lifetime measurements (Bc and various b-baryons) 900 Hz: single muon trigger Mainly triggers on semi-leptonic B decays, no bias on the other B; allows to collect unbiased B decay samples, useful to understand various systematics Data mining: reconstruction of accompanying b-hadron in modes not included in the exclusive HLT algorithms, not foreseen at the start of the experiment, or “untriggerable modes” For hadronic modes, good tagging (eff  15%) due to already detected b on other side 300 Hz: D* trigger D0K, but also D0KK,  modes Large K and  samples for RICH PID calibration Charm physics, including D0 mixing (x and yCP), CP violation in D0KK, 

Simulation and Reconstruction Full GEANT 4 simulation Complete description from TDRs Detector response Based on test-beam data (resolution, efficiency, noise, cross-talk) Spill-over effects included (25 ns bunch spacing) Trigger simulation thresholds tuned to get maximal signal efficiencies at limited output rates of 1 MHz (L0) and 40 kHz (L1) HLT simulation almost ready Offline reconstruction Full pattern recognition (track finding, RICH reconstruction, …) RICH2 RICH1 VELO TT T1 T2 T3 Geant event display No true MC info used anywhere!

Monte Carlo samples During last year many hundreds of million events were produced on the LCG GRID (see Domenico’s) Mostly minimum bias events (for fixing trigger bandwidths) bb events with inclusive decays (for assessing backgrounds in physics analyses) signal events (of course...) Still far from a complete understanding of the backgrounds (eventually will need real data...) Recently inclusive Ds events started to be produced (cc cross section 7 times larger than bb... dangerous?)

Trigger simulation Typical L0xL1 efficiencies (for offline selected events) hadronic channels: ~40% di-muons: ~70% EM channels: ~30% Exclusive HLT simulation in progress Typical efficiency ~90% Timing: L0: 3.5 s (synchronous) L1: 3 ms (max. 58 ms) L0 efficiency L1 efficiency L0L1 efficiency

Measurement of ms Need a flavour specific Bs decay to measure mixed/unmixed decays The best channel (if not limited by statistics) is BsD-s+ “Large” visible branching ratio ~ 1.2 x 10-4 BR(BsD-s+) ~ 2.8 x 10-3 BR(D-sK+K--) ~ 4.4 x 10-2 Fully exclusive reconstruction Limited background Optimal proper decay time resolution Ingredients for the measurement Good trigger efficiency for fully hadronic channels Good hadron particle ID, particularly relevant for same and opposite side kaon tagging Good tagging efficiency Good mass resolution for limiting background impact Good proper time resolution for resolving the fast Bs oscillations

Importance of RICH for K/ separation BsK+K- without RICH PID /K separation for BsDs / BsDsK RICH Particle ID extremely important for tagging using kaons BsK+K- with RICH PID BsDsK BsDs

Flavour tagging e-, m- Qvertex ,QJet Opposite side High Pt leptons K± from b → c → s Vertex charge Jet charge B0opposite K- D PV Bs0signal K+ Same side Fragmentation K± accompanying Bs ± from B** → B(*)± K- K + D2=(1-2)2: tagging power : tagging efficiency : mistag probability ~7.5 3.1 (K) 0.8 2.4 0.6 1.4 Bs ~ 4.4 0.7 (p) 0.7 2.1 1.2 Bd Same side p / K Combined Jet/ Vertex Charge Kaon opp.side Electron Muon Tag Tagging power in % (Same opposite side performance for Bd and Bs within errors)

Bs  Dsp event yield and resolutions 80k reconstructed signal/year with DsKK mode Combinatorial background from beauty events: B/S~0.3 Excellent resolutions from full GEANT simulation Proper time resolution ~40 fs Mass resolution ~14 MeV Decay length resolution ~200 mm Proper time resolution Bs invariant mass Bs decay vertex resolution Bs mass [GeV/c2]

Sensitivity on oscillation amplitude A as a function of ms Sensitivity to ms Resolution for Standard Model ms in one nominal year of data taking L=2 fb-1 (statistical only) (ms=20 ps-1) ~ 0.01 ps-1 Reconstructed Bs Ds unmixed decay rate (1 year) simulated for Dms = 25 ps-1 Bs mixing can be clearly observed 10% better t/t 1 year sensitivity much larger than SM expectations (ms~20 ps-1) Statistical significance on oscillation amplitude A above 5 for ms up to 68 ps-1 (at L=2 fb-1) Sensitivity on oscillation amplitude A as a function of ms 10% worse t/t

Road map to Dms in real life Proper time calibration with lifetime measurements from B J/y X Triggered by di-muon trigger (no displaced vertex trigger bias) Can measure acceptance: did displaced vertex trigger also fire? Establish resolution model Can measure resolution from negative side of proper time distribution Tagging calibration measuring mixing in B0J/y K*(K+p-) Establish tagging performance for opposite side taggers For same side kaon tagger no trivial calibration exists unfortunately, since one has to have measured Bs mixing before… Need to rely on Monte Carlo Lifetime with hadronic decays Learn to live with displaced vertex trigger Mixing with BsDsp All the hell together…

A comparison with CDF: Bs mixing in Bs Ds Channel Yield S/B Bs®Dsp (Ds®fp) 526±33 1.80 Bs®Dsp (Ds®K*K) 254±21 1.69 Bs®Dsp (Ds®3p) 116±18 1.01 Opposite side flavour tags (e, , jet charge): D2=(1.12±0.18)% Very low sensitivity for hadronic only Sensitivity: 0.4 ps-1

A comparison with CDF: Bs mixing in semi-leptonics Channel Yield S/B Bs®Dsln (Ds®f p) 4355±94 3.12 Bs®Dsln (Ds®K*K) 1750±83 0.42 Bs®Dsln (Ds®3p) 1573±88 0.32 Note: new D0 results with semileptonic decays and more data than CDF 610 pb-1 (D0) vs 355 pb-1 (CDF) Limit: ms>7.3 ps-1 @95% CL (current WA ms>14.5 ps-1 @95% CL) Opposite side flavour tags (e, , jet charge) D2=(1.43±0.09)% Limit: ms>7.7 ps-1 @95%CL

An exercise: a possible scenario in 2010 Assumptions B Factories will collect L=2 ab-1 two good years of data taking at LHCb (L=4 fb-1) improvements in LQCD quantities Observable Sensitivity in 2010 sin2 0.010  5o  |Vcb| 1% |Vub| 4% BK 5%  3% ms 0.3 ps-1 (syst.) sin2 0.045

2010 sensitivity to New Physics observables in |F|=2 transitions from UT fits (assuming Standard Model)   0.1 (now ~0.2) K0 sector   1.3° (now ~3°) Bd sector   0.12 (now ~0.5)   1o Bs sector   0.1 Only using the measurements from a few key LHCb Bs channels (in particular ms and sin2), the precision on NP observables for bs FCNC transitions in 2010 will be at the same level as the bd transitions! Furthermore, LHCb will provide the same measurements as the beauty factories, thus improving the precision in the Bd sector

Concluding remarks Key numbers for BsDs selection at LHCb according to full GEANT 4 simulations: Annual signal yield: 80k Background to signal ratio: 0.3 Tagging efficiency: 7.5% Proper time resolution: 40 fs LHCb resolution for ms around Standard Model prediction (ms=20 ps-1) in one nominal year of data taking (L=2 fb-1): (ms) ~ 0.01 ps-1 (statistical only) 1-year statistical significance on oscillation amplitude A above 5 for ms up to 68 ps-1 Far away from Standard Model expectations… Beauty factories are not finding clear evidence of New Physics in bd |F|=2 transitions still an important physics case is to understand whether the same happens in bs transitions (hints from bs penguins at B-factories) What prospects for New Physics discovery from |F|=2 at LHCb? In 2010, knowledge from bs transitions will be at the same level as bd !!

Backups!

Wolfenstein parametrization CKM matrix Wolfenstein parametrization , A, , 

Unitarity Triangle(s) 2: Bd mixing phase -2: Bs mixing phase : weak decay phase Im  key measurements from Bs   1 Re Im   Re

Bs mixing in SM Bs CKM factors Perturbative: NLO QCD correction W u, c, t Bs CKM factors Perturbative: NLO QCD correction Complementarity s: the larger  the easier ms: the larger  the harder Non perturbative: decay constant and bag factor from LQCD

Long track efficiency vs p Tracking Long track efficiency vs p Ghost rate vs p Momentum resolution p/p ~ 0.37% Ghost rate = 3% (for pT > 0.5 GeV)  = 94% (p > 10 GeV) T track Upstream track A typical reconstructed event VELO track Long track 26 long tracks 11 upstream tracks 4 downstream tracks 5 T tracks 26 VELO tracks Downstream track

Particle ID RICH 2 RICH 1 e (KK) = 88% e (pK) = 3% 3 radiators to cover full momentum range: Aerogel C4F10 CF4 RICH PID 2<p<100 GeV/c <(KK)> = 88% <(K)> = 3% Muon PID p>5 GeV <()> = 94% <()> = 2% Electron PID <(ee )> = 81% <(e)> = 1%

Trigger Rates Overview (just with exclusive HLT) L1-confirmation HLT Full reconstruction Level-0 Level-1 simulation in progress... 200 Hz

Breakdown of trigger and selection efficiencies for some benchmark channels

 and DGs from Bs  J/y f “El Dorado” Bs counterpart of the “Golden” mode B0  J/y KS CP asymmetry arises from interference of Bs  J/y f and Bs  Bs  J/y f measures the phase of Bs mixing Reconstruct J/y  m+m- or e+e-, f  K+K- 120,000 signal events/year with B/S~0.3 Final state is admixture of CP-even and odd contributions angular analysis of decay products required Need of angular analysis to separate the two components Likelihood is sum of CP-odd and CP-even terms L(t) = R- L-(t) (1+cos2qtr)/2 + (1-R-) L+(t) (1-cos2qtr) Fit for sin 2c, R- and DGs/Gs s(sin 2c) ~ 0.06 s(DGs/Gs) ~ 0.02 L=2 fb-1 ms=20 ps-1 @

 from Bs  DsK Ds+ K+ W+ W+ K- Bs Bs Ds- CP asymmetry arises from interference between two tree diagrams via Bs mixing: Bs  Ds+K- and Bs  Ds-K+ measures g - 2c Decay diagrams insensitive to New Physics assuming NP contributions from loops only Reconstruction using just Ds-  K-K+p- 5400 signal events/year B/S~1 1-year sensitivity on g - 2c (g - 2c) = 14o @ L=2 fb-1 and ms=20 ps-1 s Ds+ s K+ c u W+ W+ b u K- Bs Bs b c Ds- s s s s Not outstanding due to limited statistics but will enrich NP-free tree level  measurements from Bd decays 4

 from Bd+- and BsK+K- Bd/s /K /K Bd/s Bd (95%CL) BsKK (95%CL) Measure time dependent asymmetries for Bd→ and Bs→KK to determine Adir and Amix ACP(t) = Adir cos(mt) + Amix sin(mt) Adir and Amix depend on decay phase  mixing phases  or  Penguin/Tree ratio = dei Use  and  from J/Ks and J/ U-spin symmetry: d=dKK, =KK 4 observables, 3 unknowns: solve for  26k Bdpp events/year, B/S<0.7 37k BsKK events/year, B/S~0.3 s(g) ~ 5+ uncertainty from U-spin symmetry breaking Sensitive to New Physics in penguin

An exercise: a possible scenario in 2010 Observable Projection to 2010 Comment sin2 0.695 ± 0.015 B-factories at 2 ab-1  (104 ± 7)o  (54 ± 5)o B-factories at 2 ab-1 + LHCb BDK at 4 fb-1 |Vcb| (incl. + excl.) (10-3) 41.7 ± 0.4 |Vub| (incl. + excl.) (10-4) 36.4 ± 1.6 md 0.503 ± 0.003 mt 171 ± 3 CDF/D0 K 0.00228 ± 0.000013 Current value  0.2240 ± 0.0008 e.g. NA48/3 BK 0.846 ± 0.047 Lattice QCD (0.276 ± 0.014) MeV  1.200 ± 0.037 ms (20.5 ± 0.3) ps-1 LHCb BsDs at 4 fb-1 (cons. syst. added) sin2 0.031 ± 0.045 LHCb BsJ/ at 4 fb-1 -2 (52 ± 10)o LHCb BsDsK at 4 fb-1

Knowledge of CKM parameters in 2010 Scenario from UT fits allowing New Physics in |F|=2 transitions   0.02   3.5o   3o   0.02  = 0.05o   1o

How far is the Tevatron? Will CDF be able to add same-side kaon? Will D0 catch up to CDF?