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B mixing and lifetimes at the Tevatron
FPCP 2006 Vancouver Jónatan Piedra LPNHE-University Pierre et Marie Curie / CNRS-IN2P3 on behalf of the D and CDF Collaborations
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Outline Precision B Lifetimes B Mixing Summary THIS TALK OTHER TALKS
motivation Lb Bs Bs lifetime difference B Mixing current status ingredients results Summary CDF and D detectors CDF and D Hot Topics Detailed Bs mixing at D D. Buchholz D Hot Topics Detailed B hh D. Tonelli CDF Hot Topics Bc lifetime I. Kravchenko B Spectroscopy Bs Ds Ds R. Van Kooten Bs Decays and B leptonic decays April 9, 2006 J. Piedra
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Precision B Lifetimes
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Precision B Lifetimes Motivation
EXPERIMENT THEORY (NLO) C. Tarantino, hep-ph/ b-hadron decays dominated by b-quark Light quarks are included with 1/mb perturbative expansions (HQE) expect small differences between lifetimes of different species lifetime ratios reduce theory uncertainties Cecilia Tarantino, October 2003 April 9, 2006 J. Piedra
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Precision B Lifetimes Lb Lifetime
CDF and D have measured Lb J/ L lifetime Better proper time resolution than Lb Lc ln (world average dominated) Earlier t(Lb)/t(B0) predictions were 2s above experiment new calculations including higher order effects predict lower ratio D 250 pb-1 CDF 370 pb-1 PRL (2005)
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Precision B Lifetimes Lb Lifetime at CDF
Analysis based upon 370 pb-1 Technique unbinned maximum likelihood fit to proper decay-length and mass Lb J/ L0 194 23 candidates J/ mm L0 pp - Use B0 reference mode larger yield and similar decay topology B0 Jpsi Ks 53 candidates Ks0 p +p - CDF 370 pb-1 HFAG April 9, 2006
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Precision B Lifetimes Bs Lifetime
D and CDF measure lifetime in D 400 pb-1 CDF 360 pb-1 best in the world April 9, 2006
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Precision B Lifetimes Neutral Meson Mixing
Quark mixing non-diagonal Hamiltonian for Diagonalizing the Hamiltonian results in two eigenstates and two masses mH and mL, with Dm mH – mL two decay widths GH and GL, with DG GL – GH R. Van Kooten Bs decays and B leptonic decays April 9, 2006
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Precision B Lifetimes Bs Lifetime Difference
Bs J/ Pseudoscalar Vector - Vector Decay amplitude decomposed into 3 linear polarization states A0 = S + D wave P even A|| = S + D wave P even A = P wave P odd If CP violation neglected Bs,Light CP even Bs,Heavy CP odd angular distributions are different Angular analysis separates CP eigenstates measure two lifetimes April 9, 2006 J. Piedra
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Precision B Lifetimes Bs Lifetime Difference
D 800 pb-1 CDF 260 pb-1
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Precision B Lifetimes................... and
First measurement (~95% CP even) CDF 360 pb-1 D. Tonelli CDF Hot Topics Expected Lifetime extracted from decay Bs -> KK ~ 95% CP even CDF 360 pb-1 best in the world D 210 pb-1 I. Kravchenko B Spectroscopy April 9, 2006
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Precision B Lifetimes HFAG
B+ and B0 at LEP/SLC, B factories and Tevatron (CDF/D) dominated by Belle and BaBar Bs dominated by Tevatron, LEP Bc at Tevatron Lb dominated by LEP, Tevatron b-hadron species measured lifetime [ps] t/t(B0) lifetime ratio predicted range B+ 1.643 0.010 1.076 0.008 1.04 – 1.08 Bs ( flavor specific) 1.454 0.040 0.914 0.030 0.99 – 1.01 Lb 1.288 0.065 0.844 0.043 0.86 – 0.95 B0 1.527 0.008 hep-ex/ March 2006 Bc 0.469 0.065
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B Mixing
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B Mixing Theoretical Prediction
SM prediction for the ratio of Bs and B0 mixing frequencies Dmd precisely measured Dms not yet measured precisely Potential NP discovery NP = New Physics CKM fit J. Piedra
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B background candidates sct time resolution
B Mixing Significance S signal candidates B background candidates sct time resolution The dilution D measures the purity, D = 0 (1) random (perfect) tagger The dilution attenuates the observed oscillations April 9, 2006
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1. Final State Reconstruction
B Mixing Ingredients 1. Final State Reconstruction b-flavor at decay 3. b-Flavor Tagging b-flavor at production 2. Proper Decay Time In B rest frame 4. Amplitude Scan for Bs Mixing Set a lower limit or observe Dms Opposite Side Trigger Side
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B Mixing Reconstructed......................
D exploits semileptonic decays from m trigger CDF uses both electrons and muons D 1 fb-1 CDF 1 fb-1
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B Mixing Reconstructed.....................
CDF collects hadronic B decays by triggering on impact parameter Around 3700 Bs signal candidates April 9, 2006 J. Piedra
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B Mixing Proper Decay Time
Procedure measure pT of B daughter tracks measure the decay length Lxy boost B back to its rest frame Fully reconstructed decays all daughters reconstructed Partially reconstructed decays some tracks escape detection need simulation April 9, 2006 J. Piedra
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B Mixing b-Flavor Tagging
A flavor tagger determines the b-flavor at production time bb production flavor tagging on the Trigger Side or the Opposite Side Soft Lepton Tagger look for B ln DX decay on the OS lepton charge indicates b-flavor Jet Charge Tagger look for jet or secondary vertex from OS jet charge indicates b-flavor Same Side (Kaon) Tagger look for a fragmentation track on the TS it is charge correlated with the b-flavor SLT Trigger Side JQT - Jet Charge Tagger. Empirically, the sum of all particle charges in a jet containing a B meson is correlated with the b-quark charge - Same Side Tagger. Looks for the fragmentation track that is charge correlated with the produced B meson Opposite Side SS(K)T J. Piedra
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B Mixing Flavor Analysis on B+ and B0
Calibrate opposite side flavor taggers prior to Dms analysis combine several B+,0 decays combine all taggers Direct Dmd measurement cross-check for Bs mixing asymmetry combined eD2 (%) 1.55 0.08 2.48 0.22 CDF D D semileptonic 1 fb-1 Dmd = (stat) (syst) ps-1 CDF semileptonic 1 fb-1 Dmd = (stat) (syst) ps-1 CDF hadronic 355 pb-1 Dmd = (stat) (syst) ps-1 world average Dmd = ps-1
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B Mixing SSKT at CDF Look for the fragmentation track that is charge correlated with the B Dms not yet measured precisely Parameterization from MC Extensive data/MC comparisons on all tagging related quantities Rely on MC prediction of SSKT performance for Bs mixing
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CDF MC 355 pb-1 B Mixing SSKT at CDF Systematic studies cover
quark fragmentation model bb production mechanisms excited B mesons content detector / PID resolution particle species content around B data / MC agreement Select track within DR < 0.7 around B most likely to be a kaon based on dE/dx and TOF information CDF MC 355 pb-1
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B Mixing Fourier Analysis
Two domains to fit for oscillations time fit for a cosine wave frequency examine f-spectrum Time domain approach fit for Dms in P(t) ~ 1 D cos(Dmst) Frequency domain approach introduce amplitude, P(t) ~ 1 AD cos(Dmst) fit for A at different Dms obtain frequency spectrum A(Dms) standard method for combining limits with flavor taggers calibrated A = 1 for the true Dms else A = 0 time domain frequency domain
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B Mixing Amplitude Scans on Dmd
The yellow band is 1.645sA around data points Dm values where A sA < 1 are excluded at 95% CL Sensitivity is where 1.645sA = 1 D Run II Preliminary 1 fb-1 Amplitude scan works on B0 decay modes April 9, 2006
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B Mixing Amplitude Scans on Dms
A/sA (Dms = 19 ps-1) = 2.5 5% p-value SSKT not yet included A(Dms=19) = 1.6 sigma from 1 sensitivity 95% CL limit D 1 fb-1 14.1 ps-1 14.8 ps-1 sensitivity 95% CL limit CDF 355 pb-1 13.0 ps-1 8.6 ps-1 April 9, 2006 J. Piedra
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B Mixing Log Likelihood Scan
hep-ex/ submitted to Phys. Rev. Lett. 17 < Dms < 21 90% CL assuming Gaussian uncertainties
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B Mixing D Effect on World Average
HFAG preliminary (correlated systematics not included) A (Dms = 19 ps-1) 1.5 sA sA D
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Summary New Lb lifetimes reduce distance with theory
Tevatron measures the best Bs lifetimes in the world Bs lifetime difference within SM D Bs oscillation 1 fb-1 2.5 sA excess at Dms = 19 ps-1 (5% p-value) 17.1 < Dms < % CL CDF Bs oscillation 355 pb-1 Dms > 8.6 ps 95% CL
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Backup
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Precision B Lifetimes Transversity Basis
= +1 particle -1 antiparticle untagged Bs Transversity basis J/ rest frame flight direction +x KK plane xy plane J. Piedra
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B Mixing Semileptonic Decay Time
Missing particles missing pT Determine pseudo-ct from data ct = ct* kMC include kMC effect in signal PDF Very nice talk. I like the general style, very Jonatan Piedra. Ch. Paus April 9, 2006 J. Piedra
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