03/09/2008 Md. Naimuddin 1 Masses, Lifetimes and Mixings of B and D hadrons Md. Naimuddin (on behalf of CDF and D0 collaboration) Fermi National Accl. Lab Recontres de Moriond 09 th March, 2008

03/09/2008 Md. Naimuddin 2 –B physics at the Tevatron –Fermilab Tevatron –CDF and D0 Detectors –Mass measurement –Lifetimes –Mixings –Conclusions OUTLINE

03/09/2008 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% B 0 ( ) = 38% B s ( ) = 10% B c ( ) = 0.001% Rest  b baryons

03/09/2008 Md. Naimuddin 4 Fermilab Tevatron Highest Luminosity achieved: 2.92x10 32 cm/s 2 Expected: ~7 fb -1 by end of 2009

03/09/2008 Md. Naimuddin 5 CDF Detector Solenoid 1.4T Silicon Tracker SVX up to |  |<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

03/09/2008 Md. Naimuddin 6 D0 Detector 2T solenoid Fiber Tracker 8 double layers Silicon Detector up to |  |~3 forward Muon + Central Muon detectors excellent coverage |  |<2 Robust Muon triggers.

03/09/2008 Md. Naimuddin 7 Theoretical prediction of the masses E. Jenkins, PRD 55, R10-R12, (1997). Predicted mass hierarchy: M(Λ b )< M(  b ) < M(  b ) Searching for  b in  b - →J/  +  - Discovery of  b - Natural constraints in  b - →J/  +  - - 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 Reconstruction strategy for  b - Reconstruct J/  →  +  - - Reconstruct  →p  - Reconstruct  →  +  - Combine J/  +  - Improve mass resolution by using an event-by event mass difference correction.

03/09/2008 Md. Naimuddin 8 M(Ξ b - ) = ± 2.5 (stat.) ± 1.7(syst.) MeV/c 2 Significance of the observed signal: >7.0  Number of signal events: 15.2 ± 4.4 Mean of the Gaussian: ± 0.011(stat) GeV Width of the Gaussian: ± GeV Fit: Unbinned extended log-likelihood fit Gaussian signal, flat background Number of background/signal events are floating parameters Significance of the observed signal: 5.5  Discovery of  b - D0 CDF PRL 99, (2007) PRL 99, (2007)

03/09/2008 Md. Naimuddin 9  B c 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/c 2.  Recent lattice QCD calculations predict: F. Allison et. al, PRL 94, (2005) Mass measurement in B c → 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. B c Mass

03/09/2008 Md. Naimuddin 10 D0: m(B c ) = 6300  14 (stat)  5 (sys) MeV/c 2 CDF: m(B c ) =  3.2 (stat)  2.6 (sys) MeV/c 2 A total of 137 events with invariant mass between 6240 and 6300 MeV/c2 observed are attributed to Bc signal and rest to background. The distribution was fitted with a Gaussian for signal and fit returns a total of 54  12 signal candidates. From the negative log-likelihood of S+B and background only hypothesis, the signal significance was extracted to be 5.2 . 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. B c Mass hep-ex/ Hep-ex/

03/09/2008 Md. Naimuddin 11 B c lifetime Lifetime measurement in B c → J/  Theory: 0.48  0.05 ps (QCD sum rules) CDF: Most precise measurem ent to date hep-ph/  The decay property of B c mesons are influenced by presence of both b and c quarks.  Since either quark may participate in the decay, B c lifetime is predicted to be shorter than other B hadrons. Using an unbinned likelihood simultaneous fit to J/  invariant mass and lifetime distributions, a signal of 856  80 candidates estimated.

12 B s Lifetime (hadronic) 03/09/2008 Md. Naimuddin Used two decay hadronic modes of B s to measure its lifetime: B s → D s - (  - )  + : Fully reconstructed (FR) – More than 1100 events reconstructed B s → D s -  + (  +  0 ): Partially reconstructed (PR) -  0 not reconstructed.  These candidates are from actual B s 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) =  ps

03/09/2008 Md. Naimuddin 13  (Bs) =  ps Com  (Bs) =  ps  The fit procedure was tested extensively on three control samples: B 0 →D - (K +  -  - )  +, B 0 →D *- [D 0 (K +  - )  - ]  + and B + →D 0 (K +  - )  + c  (Bs) =  12.2 (stat)  7.4 (syst)  m Toy Monte Carlo studies were used to set the size of the systematic uncertainty. B s Lifetime (hadronic) FR:

03/09/2008 Md. Naimuddin 14 Lifetime in B s →J/ψ ϕ  Average lifetime of Bs, Bs(bar) system can be measured with B s → 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 psD0:  (Bs) = 1.52  0.06  0.01 ps hep-ex/ hep-ex/

03/09/2008 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 B 0 and B s 0 by UA1 and then in B 0 mesons by ARGUS in  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

03/09/2008 Md. Naimuddin 16 Charm mixing Measure mixing in D * →D 0  ; D 0 →K  x’ = x cos  K  + y sin  K  y’ = y cos  K  - x sin  K  MixingXy Bs0-Bs B0-B K0-K D0-D  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  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

03/09/2008 Md. Naimuddin 17 Result: y’ = and x’ 2 = Bayesian probability contour excludes no mixing point at 3.8 . Charm mixing BaBar y’ = , x’ 2 = Belle y’ = , x’ 2 = Alternate checks of the significance also resulted in 3.8  Likelihood ~ exp(-  2 /2) Solid point = best fit Cross = no- mixing (y’=x’=0) Open diamond = highest probability physically allowed hep-ex/

03/09/2008 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.

03/09/2008 Md. Naimuddin 19 Back-up slides

03/09/2008 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.

03/09/2008 Md. Naimuddin 21 Observation of Orbitally Excited B s2 * 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, B s2 * is reconstructed as B + K -. M(B s2 * ) = ±1.1(stat.)±0.7 (syst.)

03/09/2008 Md. Naimuddin 22 Mass measurement of orbitally excited B **0 CDF measurements: D0 measurements: m(B 1 0 ) = ±2.4(stat.) ±1.4(syst.) MeV/c 2 m(B 2 *0 ) = ±2.4 (stat.) ±1.7(syst.) MeV/c 2 B 1 → B *+  - ; B *+ → B +  B 2 * → B *+  - ; B *+ → B +  B 2 * → B +  - B 0 * (J=0), B 1 * (J=1): J q = ½, decay via S-wave  too broad (  ~ 100 MeV) to be observable. B 1 (J=1), B 2 * (J=2): J q =3/2, D-wave decay,  ~ 10 MeV m(B 2 * )-m(B 1 )  14 MeV

03/09/2008 Md. Naimuddin 23  b Lifetime  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

03/09/2008 Md. Naimuddin 24 Λ b Lifetime (semileptonic)  b →  c X;  c → K s 0 p  First K s 0 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(L T.p T (  c + ))/ |p T (  c + )| 2   c events are split into 10 visible decay length bins.  B ) = ps Combined Semileptonic and hadronic