B the Tevatron

Transcription

1 B the Tevatron Stephanie Hansmann-Menzemer Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg DESY, 9 th of November 7 xxx p.1/1

2 Tevatron p p collisions at s = 1.96 TeV observed by two experiments: CDF & D p./1

3 B Hadron Colliders + Large cross section + σ(p p bx) 1 µb + B factories: 1 nb + High center-of-mass energy + Heavy & excited B s, + e.g. B s, B c, Λ b, Ξ b,b,b s,... CDF - σ(p p X) O(1 3 ) higher - require excellent trigger - High track density - require dedicated algorithms xxxxxxxx Tevatron unique place to study large amounts of B s Mesons. BABAR p.3/1

4 B Triggers Trigger signatures: lepton (e,µ) and displaced tracks B J/ΨX; J/Ψ µ + µ + muon provides easy trigger - small branching ratio Semi-leptonic B decays + large branching ratios ( %) - missing neutrino Fully hadronic B decays + 8% of branching ratio - requires displaced track trigger Di-Muon Trigger (CDF+D) x x Lepton Trigger (D) + Displaced Track (CDF) x Two Track Trigger (CDF) x P t GeV/c; χsvt 5 x µm tracks per σ= 47 µ m Includes 33 µ m beamspot primary vertex. impact parameter B secondary vertex xxx SVT d (µm) p.4/1

5 p.5/1

6 B s Mixing Analysis CP violation in B s mixing - Γ & φ s Spectroscopy: Observation of Ξ b, B c, B s, Σ b,... Rare B decays: B s µ + µ p.5/1

7 B s Mixing B s Access to fundamental SM parameters b s V V tb ts t t V V ts tb s b B s m s = G F 6π η B m Bs ˆBBs f B s M W S( m t m W Hadronic uncertainties are canceling out ) V ts V tb m s m d = m Bs m Bd ξ V ts V td _ b Z, _ s Prerequisite for time dependent CPV Possible contributions from New Physics s b p.6/1

8 B s B s Mixing Analyses opposite side signal side + π b hadron xxx 1) B s reconstruction/selection ) Proper time measurement PV L xy ct = L xy mb pt B s D s K + π K 3) Flavour tagging (main challenge at hadron colliders) Time dependent asymmetry: A(t) N(t) mixed N(t) unmixed N(t) unmixed +N(t) mixed = D cos( m s t), D = 1 P mistag p.7/1

9 B s Mixing is extremely fast! Mixed Asymmetry B d mixing m d =.5 ps 1 B s mixing m s = ps proper decay time, t [ps] SǫD significance: S sσ ct ) S+B e ( m Requirements High vertex resolution High momentum resolution Many signal events Good tagging performance p.8/1

10 Hadronic B s Channels candidates per 1 MeV/c xxxxxx -1 CDF Run II Preliminary L = 1. fb data φπ -π - mass [GeV/c ] fit + - B D π - s s /K *+ - B D π - s s /K B D + ρ - s s + b D s X + B D + Λ b Λ c π - π - comb. bkg. Golden Channel decay # B s D s (φπ)π B s D s(φπ)π, B s D s (φπ)ρ 3 B s D s (K K)π 14 B s D s (3π)π 7 B s D s (φπ)3π 7 B s D s (K K)3π 6 B s D s (3π)3π Hadronic modes selected by Two Track Trigger! p.9/1

11 B s ld s X Decays CDF Run II Preliminary 1 candidates per MeV/c 5 data fit B s signal false lepton & physics + D reflection comb. bkg. -1 L 1 fb probability density 1 5 CDF Run II (*) all B s D s l ν. < m Ds l 3.1 GeV/c 4.3 < m Ds l 4.5 GeV/c 4.9 < m Ds l 5.1 GeV/c * B s D s B s π D s ρ B s * l D s (K K) X mass [GeV/c ] D s Reconstructed κ = p T /p T B s 61.5 semileptonic B s decays High statistic, low proper time resolution: ct = L xym(b) p T (B) = L xym(b) p T (ld) K p.1/1

12 Flavour Tagging K + l Opposite Side Tagging ǫd = 1.8 % b B s xxxxxx Same Side Tagging x b b s/d s/d u u B s/d + + K /π ǫd (had.) = 3.8 %,xxx ǫd (semil.) = 4.8 % p.11/1

13 Amplitude Scan Amplitude data ± 1 σ σ data ± σ data ± σ (stat. only) sensitivity 31.3 ps m s 1 [ps ] Probability of fluctuation > 5 σ m s = ±.1(stat.) ±.7(syst.) ps 1 (PRL 97, 43(6)) p.1/1

14 Is This Visible? All events with tagging dilution > 1% Weighted events (tagging dilution, σ ct, S/B...).4 Data Unbinned fit CDF Run II Preliminary -1 L = 1. fb Raw asymmetry. -. Fitted Amplitude 1-1 data proper time mod(17.77 ps ) [cm] - cosine with A= Decay Time Modulo π/ m s [ps] xxxxxunbinned likelihood fit p.13/1

15 Result on V td / V ts η excluded area has CL >.95 sin β ε K xxxsummer 5 m d γ α m s & m d sol. w/ cos β < (excl. at CL >.95).1 V ub /V cb γ β ρ α C K M f i t t e r EPS 5 η xxxxxxxxx autumn 6 f i t t e r.6 BEAUTY 6 excluded area has CL >.95 γ sinβ ε K m d m s & m d α.1 γ α V ub /V cb β ρ ε K sol. w/ cosβ < (excl. at CL >.95) α CKM γ xxx V td / V ts =.61 ±.7 (exp.) (theo.) (hep-ex/749) consistent with direct measurements - dominated by theoretical uncertainties p.14/1

16 Mixing & CP Violation b V tb t V ts s B s s V ts t V tb b B s flavor eigenstates B & B mass eigenstates B H & B L x 1) m = m H - m L x ) Γ = Γ L - Γ H x 3) CP violation in mixing: φ if φ = mass eigenstates CP eigenstates CP(B H ) = +1 (CP even),x CP(B L ) = 1 (CP odd) SM prediction: Γ =.1 ±.3 ps 1, φ = -.3 ±.5 (hep-ph/463) p.15/1

17 B s J/Ψφ P V V decay: polarization states CP eigenstates A : S + D wave P even A : S + D wave P even A : P wave P odd without CP violation: B s,l CP even B s,h CP odd µm Candidates per Data Total Fit Total Signal CP even CP odd Background 5 15 CP even A, A 1 5 Data Total Fit Total Signal CP even CP odd Background ct (cm) CP odd A Transversity p.16/1

18 Γ s = φ s = (fixed) (stat.) ±.6 (syst.) ps 1 With tagging, expected 1.5 improvement on uncertainties Still 4 more data ahead ] -1 Γ [ps CDF II Preliminary Theoretical Pred.: (hep-ph/61167) -1 Γ=(.96±.39 ps )cosφ s Standard Model Confidence Region: 95% 9% L=1.7 fb -1 Γ (1/ps) DØ, 1.1 fb B s J/ψ φ -.3 SM -.4 Γ = Γ SM cos(φ s ) φ s (radians) Γ s =.17 ±.9 (stat.) ±. (syst.) ps 1 φ s = -.79 ±.56 (stat.) (syst.) φ s p.17/1

19 B the Tevatron Triggers crucial for any hadron colliders Very successful B program in challenging environment: m s = ±.1 (stat.) ±.7 (syst) ps 1 First measurement of the mixing parameters Γ and φ s Observation of B hadrons: Ξ b, Σ b, B c, λ b, B s,..... Hadron colliders are precision measurement experiments Further interesting results expected with up to 6 fb 1 p.18/1

20 Backup p.19/1

21 CDF versus D CDF Two displaced Track Trigger (TTT) Particle ID (de/dx & TOF) Forward Mini drift chamber Central Scintillator Forward Scintillator Silicon layer close to interaction Shielding strong in hadronic decays good kaon tagging New Solenoid, Tracking System Si, SciFi, Preshowers D + New Electronics, Trig, DAQ Excellent Muon coverage High forward acceptance strong in semi-muonic decays excellent muon tagging p./1

22 FCNC: B s(d) µ + µ SM: no tree level contribution, loops strongly suppressed BF(B s µ + µ ) = BF(B d µ + µ ) = G. Buchalla, A. Buras, Nucl. Phys. B398,85 SM extensions predict up to 1 higher rates Each signal would be hint to new physics! CDF results (1.9 fb 1 ): BR(B s µ + µ ) % CL BR(B d µ + µ ) % CL D results (. fb 1 ): BR(B s µ + µ ) % CL xx p.1/1