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Jet Results

This study investigates hadronic jets at high energies and their agreement with Standard Model predictions. It explores the potential signal of quark compositeness and the role of gluon content in matching experimental data. Additionally, it examines b-quark production and decay, along with the potential for measuring elements of the CKM matrix.

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Jet Results

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  1. Jet Results HADRONIC JETS F. Bedeschi, INFN-Pisa

  2. Hadronic jets • High Et jet at D0 in Run 1 • Et1 = 475 GeV • Et2 = 472 GeV • h1 = -0.69 • h2 = 0.69 • Side view F. Bedeschi, INFN-Pisa

  3. Hadronic jets EM calorimeter energy Hadronic calorimeter energy • High Et jet at CDF in Run II • Et1 = 403 GeV, Et2 = 322 GeV • h1 = 0.037, h2 = -0.364 • “Lego plot”: • f vs. h • R-f view Each cell is a calorimetric tower F. Bedeschi, INFN-Pisa

  4. Inclusive jets • Jet Et cross sections match quite well SM predictions over several orders of magnitude CDF D0 F. Bedeschi, INFN-Pisa

  5. Inclusive jets • CDF observed an excess in the high end of the spectrum • Such an excess could be a signal of quark compositeness! • D0 did not see a clear effect • After a detailed comparison with theory… however F. Bedeschi, INFN-Pisa

  6. Inclusive jets • After years of work and discussions: • Effect is related to pdf choice (newer pdf’s do better) • CDF and D0 agree CDF data F. Bedeschi, INFN-Pisa

  7. Inclusive jets • Conclusion is that one has to boost gluon content at high x to match CDF and D0 data with theory. • Can be done without conflicts with previous data of other experiments • Happens naturally with latest sets of pdf’s including Tevatron jet data F. Bedeschi, INFN-Pisa

  8. Jets and pdf’s • Tevatron extends coverage to high values of x, Q Tevatron HERA Fixed target F. Bedeschi, INFN-Pisa

  9. Jet angular distribution • Jet angular distributions are less sensitive to details of pdf’s • Best compositeness limits set with this method • No effect observed c = (1+cos q*)/(1-cos q*) q* = polar angle in jet system center of mass F. Bedeschi, INFN-Pisa

  10. Future of jet physics • Run 1 – 87/pb • Run IIA – 2/fb • Run IIB – 15/fb • Can probe much higher jet energies • Look for new excesses in the high end of the spectrum Run IIB Run IIA Run 1 Run IIA Run IIB F. Bedeschi, INFN-Pisa

  11. Jet Summary • What did we learn? • Jets are an experimental signature of quarks and gluons • Jet production tests the SM predictions for quark and gluon interaction dynamics • Jet production at the Tevatron is sensitive to pdf’s in a region not fully covered by other experiments • Deviations from SM predictions that cannot be absorbed in the pdf’s can signal new physics. In particular quark compositness • SM model will be tested at an even deeper level with data collected during the ongoing Run II of the Tevatron F. Bedeschi, INFN-Pisa

  12. b-quarks b-quark production and decay F. Bedeschi, INFN-Pisa

  13. b-quarks • b-quarks are the second heaviest quarks observed • Mb ~ 5 GeV/c2 can still be copiously produced at Tevatron • sb ~ 100 mb (cfr. sb ~ 1 nb at B-factories, ~ 5 nb at LEP) • S/N ~ 10-3 (cfr. 0.2 at B-factories, 0.14 at LEP) • Interest of b-quarks: • Production: test SM production in region with a different characteristic mass scale • Mass protects calculations from infrared and collinear divergences • Decay: ideal for measuring elements of CKM matrix which couple to third generation quarks • Mixing (|Vtd|, |Vts|) • CP violation (arg(Vtd), arg(Vub)) F. Bedeschi, INFN-Pisa

  14. l - n W- b B c q D q J/Y c b c W- s B K q q b-quark production • How do I tell I made a b-quark? • Charm mesons, D, in decay products • Leptons from SL decay: • ~10% for each mode • Large mass  large ptrel • Leptons from J/Y decay: • B  J/Y + X 1% • J/Y  m+ m-, e+ e- 6% each • Secondary vertex: • ct ~ 450 mm • <Nch> ~ 5 F. Bedeschi, INFN-Pisa

  15. A real B event F. Bedeschi, INFN-Pisa

  16. b-quark samples D0 K-p+ D*+ D0 p+ D0 K-p+ • Charm signals in events with leptons • Sign of lepton correlated with that of kaon • Shaded area corresponds to wrong sign combinations D*+ D0 p+ D0 K- 3p D*+ D0 p+ D0 K-p+ p0 F. Bedeschi, INFN-Pisa

  17. B+y K+ b-quark samples Y mm • Exclusive B decays with J/y and kaons B0y K0* F. Bedeschi, INFN-Pisa

  18. b-quark production • b-quark production: • Leading order ~ next-to-leading order LO NLO F. Bedeschi, INFN-Pisa

  19. b-quark production • Observed x-sections are higher than SM predictions by ~factor 2.5 – 3 • Much work to understand this b-quark cross section Good consistency observed between CDF and D0 results F. Bedeschi, INFN-Pisa

  20. b-quark production B+ meson cross section • Recent developments (Cacciari et al.) suggest that this can be improved with better fragmentation CDF data F. Bedeschi, INFN-Pisa

  21. q1 q2 W- b B c q D q B hadron decays • B hadron decays dominated by b-quark decay • Effect of spectator quarks can be included with perturbative expansions in terms of 1/mb • Expect small differences between lifetimes of different species • Measurement of lifetimes test accuracy of these methods and the SM F. Bedeschi, INFN-Pisa

  22. B-hadron decays • Lifetime summary and example Bu B+ F. Bedeschi, INFN-Pisa

  23. b-quark decays: CKM matrix • CKM matrix describes flavor mixing in charged weak current transitions • All up-type quarks (u, c, t) can couple with any down-type quarks with a strength modulated by the elements of the CKM matrix Vub = |Vub |e-ig Vub Vus Vud u Only 2 elements are complex Vcs CKM matrix = Vcd Vcb Vub b Vtd Vts Vtb W Vtd = |Vtd |e-ib CKM matrix must be unitary if there are only 3 generations F. Bedeschi, INFN-Pisa

  24. b-quark decays: CKM matrix • If CKM unitary can be expressed in powers of Vus = l = sin(qCabibbo) ~ 0.22 • Wolfenstein representation • Measurement of CKM elements allows test of unitarity  triangle is closed • 1st, 3rd col.: VudVub*+VcdVcb*+VtdVtb*=0 • Other triangles less interesting • Let: Vud = 1, Vcd = -l, Vtb = 1 • Vub*+ Vtd = l Vcb*O (3%) • Divide byAl3=l Vcb*=-l Vts Vtd l Vts Vub* l Vcb Charmless Mixing a (1-r-ih) (r+ih) h g b r 1 Angles: CP violation F. Bedeschi, INFN-Pisa

  25. b-decays: CKM matrix • Vub/Vcbis related to fraction of b-hadron decays with no charm in final state • Hard to measure at hadron colliders. Done at CLEO, LEP, B-factories • Vtd/Vtsis related to an effect called mixing (see later) • Hadron colliders are very competitive and are the only place where Vts can be measured directly • The angles of the triangle are related to CP violation effects (see later) • Hadron colliders and B-factories complement each other in these difficult measurements F. Bedeschi, INFN-Pisa

  26. b W d, s u c t u c t Bd,s Bd,s d, s b W b d, s u c t W Bd,s Bd,s W d, s b u c t b-decays: mixing • Some probability that a B0 turns into a B0 due to higher order box diagrams • Dm  mt2 |Vtd,s|2 • x = tDm F. Bedeschi, INFN-Pisa

  27. Nnomix(t) - Nmix(t) Nnomix(t) + Nmix(t) b-decays: mixing • Typically what is measured is the mixing asymmetry evolution with proper decay time: • A == cos(Dm t) (t = proper time lived) • How do we know if B0 has mixed or not? • Type of B0 at time of decay defined by final state • E.g. B0 D l+n : sign of lepton tags the B type • Type of B0 at production is much harder! • Use several methods of “flavor tagging” (see later) • Such methods are not perfect: • w = probability to mistag • D = dilution = 1-2w • Finite efficiency = e • Observed asymmetry: Aobs(t) = D A(t) = D cos(Dm t) • Amplitude measures dilution • Frequency measures mixing F. Bedeschi, INFN-Pisa

  28. Flavor tagging Same side p/K Signal side • Opposite side techniques: • b-quarks are produced in pairs by the strong force that conserves flavor: always one b and one anti-b • Determine the type of the second b in the event at the decay • Mixing of the second b contributes to the dilution • Use signatures like sign of lepton, kaon (from charm decay), jet charge (estimator of leading quark charge) • Same side techniques: • Sign of nearby p has sign correlated to b type Opposite side B Jet Q tag Lepton/K Q tag F. Bedeschi, INFN-Pisa

  29. b-quark decay: mixing • Only B0 mix! • Do not want to violate charge conservation • 2 possibilities: B0d, B0s • |Vtd|2 ~ l2|Vts|2 ~ 0.05 |Vts|2 Dmd << Dms • B0d mixing measured extensively • B0d easier to produce • Mixing frequency slow  no special resolution needs • No observation of B0s mixing so far • Smaller cross section • High mixing frequency  need very good vertex resolution F. Bedeschi, INFN-Pisa

  30. b-quark decay: Bd mixing • Example: • CDF measurement of mixing • Signal: B0d D(*)- + X • Sign of D  flavor at decay • Flavor tag: opposite side lepton • Sign of lepton  flavor at production F. Bedeschi, INFN-Pisa

  31. b-decay: Bd mixing • Summary of Tevatron Run 1 B0d mixing results and comparison with LEP • Current world average dominated by Belle/BaBar:Dmd = 0.496 ± 0.007 (ICHEP 1998) (1998) F. Bedeschi, INFN-Pisa

  32. b-decay: Bs mixing • Extracting the CKM matrix elements from Dm has many theory uncertainties: • fBd and BBd are both known to ~ 15% from lattice calculations • Ratio x = fBs BBs/fBd BBd ~ 1.160.05 • The ratio |Vts|/ |Vtd| can be measured with much less theory uncertainty (~ 4-5%) • Much expectation for Dms measurement at Tevatron F. Bedeschi, INFN-Pisa

  33. Nnomix(t)-Nmix(t) Nnomix(t)+Nmix(t) b-decay: Bs mixing (prospects) • Measure mixing asymmetry • Amix (t) = • Fit to a(t) = D cos(xs t/t) Significance of measurement related to depth of likelihood minimum relative to x =  F. Bedeschi, INFN-Pisa

  34. b-decay: Bs mixing (prospects) • Signal (N): • Need all charged hadronic mode for resolution and statistics  secondary vertex trigger is essential • Bs Dsp, Ds 3p  • D+s  f p+, K0* K+, K0S K+ • Expectations for Run IIA in 2 fb-1: • 20,000 events (P-909) • 75,000 Yellow Book • S/B: • ~ 1:1 from Run I extrapolations • Assume 1:2 – 2:1 range • Small effect on significance CDF preliminary Run II data Few pb-1 F. Bedeschi, INFN-Pisa

  35. b-decay: Bs mixing (prospects) • Flavor tagging eD2: • Expect 5.7 % from Run I(6.3% measured in sin(2b) analysis) • +3.2% (SS Kaon) + 2.4% (OS Kaon) = 11.3% total • Proper Time Resolution: • Assume 45 fsec (perfect L00) to 70 fsec (L00 doesn’t work) F. Bedeschi, INFN-Pisa

  36. 5s xs reach Yellow Book 2000 Luminosity 5s xs reach BTB PAC proposal Luminosity b-decay: Bs mixing (prospects) • 5s xs significance as a function of the available luminosity • Xs mixing parameter should be within reach rather soon • The two curves refer to two extreme values of the ct resolution: • L00 proposal • L00 not usable • Red line is the SM central value • Orange line are current 95% CL limits from combined analyses (hep-ph/0112133) • With 2 fb-1 expect reach ~ 60 with conservative assumptions F. Bedeschi, INFN-Pisa

  37. b-decay: CP violation • CPviolation: G(Bf)  G(Bf) • Special simplest case f is CP eigenstate • e.g. f = J/y K0S f B0 f B0 e-i2b mix ei2b B0 mix B0 • Direct and mixed path interfere b W d, s A(BdBd) mt2 Vtd2 ~ |A|ei2b A(BdBd) mt2 V*td2 ~ |A|e-i2b u c t u c t Bd Bd d b • Asymmetry measures sin(2b) • ACP= = sin(2b) sin(Dmdt) W G(B0 f) -G(B0 f) G(B0 f) + G(B0 f) F. Bedeschi, INFN-Pisa

  38. b-decay: CP violation • As usual one measures: • Aobs(t) = D ACP(t) = Dsin(2b) sin(Dmdt) • Important to calibrate dilution with mixing analyses • Typical CP eigenstates have small Branching Ratio’s ~ 10-5! • Large b x-section at Tevatron is very useful • CDF Run 1 measurement is not competitive with B-factories, but it is very useful to estimate our future capabilities in Run II Measurements of sin(2b) as of March 2002 F. Bedeschi, INFN-Pisa

  39. + 0.37 • sin(2b) = 0.91 - 0.36 b-decay: CP violation • CDF Run 1 result is based on: • ~ 400 B0 J/y K0S • All available taggers: • Opposite side: lepton, Jet-charge • Same side: pion charge correlation • Result: ~ 400 B  y K0S Asymmetry Vs. lifetime F. Bedeschi, INFN-Pisa

  40. + + 2 1 x 1 N B d b » d ( sin (2 ) ) x N e 2 D N d b-decay: CP violation (prospects) • Extrapolation based on analytic formula for the error on the time integrated asymmetry: • In addition we account for improvements made by studying the time evolution • Expectations in 2 fb-1: F. Bedeschi, INFN-Pisa

  41. b-decay: CP violation (prospects) May 2002 • Tevatron experiments can become competitive with B factories within a few years on this measurement F. Bedeschi, INFN-Pisa

  42. CKM matrix current status Compatibility between various measurements indicates consistency with SM predictions (May 2002) This test will be much stronger after Bs mixing will be measured and more accurate measurements of sin(2b) will be available. F. Bedeschi, INFN-Pisa

  43. b-quark Summary • What did we learn? • b-quarks are heavy, but not to heavy to prevent copious production rates: • Excellent window over third generation • b-quark production has been puzzling for some time, but more accurate use of NNLO calculations and fragmentation functions partially reduces the problem • Some fundamental parameters of the SM model, in particular the modulus and the phase of the elements of the CKM matrix coupling to the third generation can be measured studying B mesons • Measurements of mixing and CP violation at the Tevatron will contribute significantly to a better understanding of this part of the SM F. Bedeschi, INFN-Pisa

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