Masses, Lifetimes, and Mixings of B and D Hadrons at the Tevatron

1. Md. Naimuddin (on behalf of CDF and D0 collaboration) Fermi National Accl. Lab Recontres de Moriond 09th March, 2008 Masses, Lifetimes and Mixings of B and D hadrons Md. Naimuddin

2. OUTLINE • B physics at the Tevatron • Fermilab Tevatron • CDF and D0 Detectors • Mass measurement • Lifetimes • Mixings • Conclusions Md. Naimuddin

3. B Physics at the Tevatron • The “beauty”- b quark: Second heaviest quark amongst the quark family – discovered at Fermilab in 1977, in a fixed target experiment. • Produced at the Tevatron in abundance via three main processes: • quark-anti quark annihilation gluon fragmentation flavor excitation B hadrons – Produced as a result of hadronization of b quark B+( ) = 38% B0( ) = 38% Bs( ) = 10% Bc( ) = 0.001% Rest b baryons Md. Naimuddin

4. Fermilab Tevatron Highest Luminosity achieved: 2.92x1032 cm/s2 Expected: ~7 fb-1 by end of 2009 Md. Naimuddin

5. CDF Detector • Solenoid 1.4T • Silicon Tracker SVX • up to |h|<2.0 • SVX fast r- readout for trigger • Drift Chamber • 96 layers in ||<1 • particle ID with dE/dx • r- readout for trigger • Time of Flight • →particle ID Md. Naimuddin

6. D0 Detector • 2T solenoid • Fiber Tracker • 8 double layers • Silicon Detector • up to |h|~3 • forward Muon + Central Muon detectors • excellent coverage ||<2 • Robust Muon triggers. Md. Naimuddin

7. Discovery of b- Theoretical prediction of the masses Predicted mass hierarchy: M(Λb)< M(b) < M(b) E. Jenkins, PRD 55 , R10-R12, (1997). Searching for b in b-→J/+- Natural constraints in b-→J/+- Reconstruction strategy for b - The final state particles (p, -, ) have significant Impact parameter with respect to the interaction point. - - has a decay length of few centimeters. -  has a decay length of few centimeters. - b has a decay length of few hundred microns, PV separation - Reconstruct J/→+- - Reconstruct →p - Reconstruct→+ - Combine J/+  - Improve mass resolution by using an event-by event mass difference correction . Md. Naimuddin

8. Discovery of b- • Fit: • Unbinned extended • log-likelihood fit • Gaussian signal, • flat background • Number of • background/signal • events are floating • parameters Number of signal events: 15.2 ± 4.4 Mean of the Gaussian: 5.774 ± 0.011(stat) GeV Width of the Gaussian: 0.037 ± 0.008 GeV PRL 99, 052001 (2007) CDF M(Ξb-)  = 5792.9 ± 2.5 (stat.) ± 1.7(syst.) MeV/c2 Significance of the observed signal: >7.0 PRL 99, 052002 (2007) D0 Significance of the observed signal: 5.5 Md. Naimuddin

9. Bc Mass • Bc system consists of two heavy quarks. • Each can decay quickly. • Non-perturbative QCD effects are not well understood. • Measurement of the production properties are expected to provide test of theoretical calculations. • Mass of Bc is not well known theoretically and has been estimated using potential models and QCD sum rules. Varies from 6150 to 6500 MeV/c2. • Recent lattice QCD calculations predict: F. Allison et. al, PRL 94, 172001 (2005) Mass measurement in Bc → J/ • CDF and D0 both uses this channel to measure the mass. • The CDF result is based on 2.2 fb-1 and D0 on 1.3 fb-1. Md. Naimuddin

10. Bc Mass The distribution was fitted with a Gaussian for signal and fit returns a total of 5412 signal candidates. A total of 137 events with invariant mass between 6240 and 6300 MeV/c2 observed. 80.4 are attributed to Bc signal and rest to background. hep-ex/0802.4258 D0: m(Bc) = 630014 (stat)5 (sys) MeV/c2 Hep-ex/0712.1506 From the negative log-likelihood of S+B and background only hypothesis, the signal significance was extracted to be 5.2. CDF: m(Bc) = 6274.13.2 (stat)2.6 (sys) MeV/c2 Using toy MC the signal significance was extracted to be larger than 8. • Both the results are in agreement with each other and also in agreement with the most precise lattice QCD predictions. Md. Naimuddin

11. Bc lifetime • The decay property of Bc mesons are influenced by presence of both b and c quarks. • Since either quark may participate in the decay, Bc lifetime is predicted to be shorter than other B hadrons. Theory: 0.48 0.05 ps (QCD sum rules) hep-ph/0308214 Lifetime measurement in Bc → J/ Most precise measurement to date Using an unbinned likelihood simultaneous fit to J/ invariant mass and lifetime distributions, a signal of 85680 candidates estimated. CDF: Md. Naimuddin

12. Bs Lifetime (hadronic) • Used two decay hadronic modes of Bs to measure its lifetime: • Bs → Ds- (-) +: Fully reconstructed (FR) – More than 1100 events reconstructed • Bs → Ds-+ (+0): Partially reconstructed (PR) • - 0 not reconstructed. • These candidates are from actual Bs • mesons so they contribute to lifetime • measurement and double the available • statistics. • Lifetime determined in two steps: First fit mass to determine relative fraction in different modes • Fit the proper decay time of Bs candidate. • K-factor multiplied to correct for missing tracks or wrong mass assignment for partially reconstructed events PR (Bs) = 1.5450.051 ps Md. Naimuddin

13. Bs Lifetime (hadronic) • The fit procedure was tested extensively on three control samples: • B0→D-(K+--)+, B0→D*-[D0(K+-)-]+ and B+→D0(K+-)+ Com (Bs) = 1.5180.025 ps FR: (Bs) = 1.4560.067 ps c(Bs) = 455.012.2 (stat)  7.4 (syst) m • Toy Monte Carlo studies were used to set the size of the systematic uncertainty. Md. Naimuddin

14. Lifetime in Bs→J/ψϕ • Average lifetime of Bs, Bs(bar) system can be measured with • Bs → J/ decay. • Average lifetime s = 1/s, where s = (H+L)/2 • CDF results are based on 1.7 fb-1 and D0 on 2.8 fb-1 data. CDF: (Bs) = 1.520.040.02 ps D0: (Bs) = 1.520.060.01 ps hep-ex/0712.2348 hep-ex/0802.2255 Md. Naimuddin

15. Mixing • Mixing: The transition of neutral particle into it’s anti-particle, and vice versa. • First observed in the K meson system. • In the B meson system, first observed in an admixture of B0 and Bs0 by UA1 and then in B0 mesons by ARGUS in 1987. • In the Bs system, first double sided bound measurement was announced right here by D0 and then it was observed and discovered in 2006 at CDF. • In the D meson system first observed by Belle and BaBar and was announced here last year. • Mixing occurs when mass eigenstates have different masses or decay widths. Characterized by mixing parameter: Mean lifetime Md. Naimuddin

16. Charm mixing • Value of x, y much larger compared to SM will hint a signal of New Physics. • To measure charm mixing, we need: • Proper decay time for time evolution • Identify charm at production • Identify charm at decay Measure mixing in D*→D0; D0→K • Identify the right sign (when pions are of same charge) and wrong sign (when pions are of opposite charge). • Get the ratio of WS to RS (with x, y << 1, i.e. assuming no cp violation x’ = x cosK + y sinK y’ = y cosK - x sinK Md. Naimuddin

17. Charm mixing • Likelihood ~ exp(-2/2) • Solid point = best fit • Cross = no-mixing (y’=x’=0) • Open diamond = highest probability physically allowed Result: y’ = 0.0085 and x’2 = 0.00012 Bayesian probability contour excludes no mixing point at 3.8. BaBar y’ = 0.0097, x’2 = -0.00022 Belle y’ = 0.0006, x’2 = 0.00018 hep-ex/0712.1567 Alternate checks of the significance also resulted in 3.8 Md. Naimuddin

18. Conclusions • Tevatron is performing quite well and we are collecting more than 100 pb-1 (equivalent of total run 1 data) of data every month. • New particles are discovered and the measurements are becoming more and more precise. • Uncertainties are still mostly statistically dominated, will reduce with more data. • Unique and strong B physics program as many of the B species are produced only at Teavtron and proves complimentary to B factories. • On our way to double our current data set by the end of 2009. Md. Naimuddin

19. Back-up slides Md. Naimuddin

20. Data Taking Excellent performance by the Tevatron and anti-proton stacking rate. Total data will be doubled in the next couple of years. Md. Naimuddin

21. Observation of Orbitally Excited Bs2* • An excited state of bs(bar) system. • When properties of this system compared with the properties of bu(bar) and bd(bar) provides good test of various models of quark bound states. • Decay via D-wave process (L=2). • In this analysis, Bs2* is reconstructed as B+K-. M(Bs2*) = 5839.6±1.1(stat.)±0.7 (syst.) Md. Naimuddin

22. Mass measurement of orbitally excited B**0 B1 → B*+-; B*+ → B+ B2* → B*+-; B*+ → B+ B2* → B+- B0*(J=0), B1*(J=1): Jq = ½, decay via S-wave  too broad (  ~ 100 MeV) to be observable. B1(J=1), B2*(J=2): Jq =3/2, D-wave decay,  ~ 10 MeV m(B2*)-m(B1)  14 MeV CDF measurements: D0 measurements: m(B10) = 5720.6±2.4(stat.) ±1.4(syst.) MeV/c2m(B2*0) = 5746.8±2.4 (stat.) ±1.7(syst.) MeV/c2 Md. Naimuddin

23. bLifetime • Before Tevatron run2, theory and experiment did not agree “b lifetime puzzle”. • World average was dominated by LEP semileptonic measurements. Significant improvement since then, theory has included NLO calculations, but experiments still have large uncertainties • important to revisit this with data sets now available at the Tevatron b →J/ ~ 10-4 Md. Naimuddin

24. Λb Lifetime (semileptonic) • b→cX; c→ Ks0p • First Ks0 are reconstructed from two oppositely charged tracks that are assigned pion mass. • 4.4K c+ events are reconstructed. • Define visible proper decay length M = mc(LT.pT(c+))/ |pT(c+)|2 • c events are split into 10 visible decay length bins. Combined Semileptonic and hadronic (LB ) = 1.251- 0.096 + 0.102 ps Md. Naimuddin