Inclusive b-quark and upsilon production in D Horst D. Wahl Florida State University DIS 2005,...

Click here to load reader

download Inclusive b-quark and upsilon production in D Horst D. Wahl Florida State University DIS 2005, Madison.

of 40

  • date post

    19-Jan-2018
  • Category

    Documents

  • view

    213
  • download

    0

Embed Size (px)

description

Tevatron – data taking l peak luminosity in 2005 above cm -2 s -1 l DØ collected > 690 pb -1 l Results shown use pb -1

Transcript of Inclusive b-quark and upsilon production in D Horst D. Wahl Florida State University DIS 2005,...

Inclusive b-quark and upsilon production in D Horst D. Wahl Florida State University DIS 2005, Madison Outline l Tevatron and D detector Bottomonium (1S) production l High p t -tagged jet production l conclusion Tevatron data taking l peak luminosity in 2005 above cm -2 s -1 l D collected > 690 pb -1 l Results shown use pb -1 Leading order Flavor creation Next to leading order Flavor excitation Gluon splitting Recent developments l Beyond NLO: resummation of log(p t /m) terms FONLL l Changes in extraction of fragmentation function from LEP data l New PDFs l Improved treatment of experimental inputs (use b-jets and b-hadrons instead of b-quarks) Open Heavy Flavor Production l Long-standing discrepancies between predicted and measured cross sections now resolved; e.g. Cacciari, Frixione, Mangano, Nason, Ridolfi,JHEP 0407 (2004) 033 l combined effects of better calculations (Fixed order (NLO)+ NLL= FONLL) relationship/difference between e+eand hadron colliders different moments of FF relevant better estimate of theory errors (upward!) new appreciation of issues withquark-level measurements l Total Cross sections (from CDF): inclusive b cross section: |y 8 GeV = 1 (-1) 100% transverse (longitudinal) polarization The vast majority of our (1S) has p T ( ) < 8 GeV Theory predicts that if there is polarization it will be at large p T. l No evidence for polarization in our signal (|y| < 1.8); not enough data for a fit in the forward region alone. l estimated the effect of (1S) polarization on our cross-section: Even at = 0.3 the cross-section changes by 15% or less in all p T bins. same effect in all rapidity regions. Question: Why is CDF's systematic error so much smaller than ours ? l Better tracking resolution --- CDF can separate the three resonances: Variations in the fit contribute considerable both to our statistical and systematic error. We believe we have achieved the best resolution currently feasible without killing the signal l Poor understanding of our Monte-Carlo and the resulting large number of correction factors. l Signal is right on the trigger turn-on curve. Conclusions (1S) cross-section Presented measurement of (1S) cross section BR() for 3 different rapidity bins out to y( ) = 1.8, as a function of p t ( ) First measurement of (1S) cross-section at s = 1.96 TeV. Shapes of d/dp t show very little dependence on rapidity. Normalized d/dp t is in good agreement with published results (CDF at 1.8TeV) l -tagged jet cross section: Measured d/dp t in central rapidity region |y| 4 GeV) f B Frac B (Pt > 4 GeV) L Luminosity p t Pt bin width HF HF cross-section bg background cross-section Jet + (Pt > 5 GeV) Correlated p13 p14 Analysis Summary Inclusive -tagged jet l corrJCCB (0.5 cone jets) Standard Jet quality cuts, Standard JET Triggers l Jet tagged with MEDIUM muon (more on this later) R( , jet) < 0.5 l |y jet | < 0.5 l JES 5.3 l Long term goal was b-jet xsec. Difficult due to no data-driven determination of b-fraction. p14 Skimming l Start with CSG QCD skim l Turn into TMBTrees (40M eventson disk) l Skim on Trees Remove bad runs (CAL, MET, SMT, CFT, JET, Muon) Remove events w/o 2 jets Use Ariel d0root_ based package SKIM 1: 1 leading jet has ~ MEDIUM (P ( ) > 4 GeV) SKIM 2: 1 leading jet has ~ loose SVT p14 All Data: CSG Skims Bad runs & lumblk removed in luminosity. Only bad run removed in event counts for skims. Up until Run (07-JUN), V12.37. Trigger Turn On Jet Trigger Collinear muon |y jet | < 0.5 Luminosity weighted Statistics uncorrelated poisson (wrong, of course) JES corrected (5.3) Efficiency Detail Value TT Trigger Eff PV Primary Vertex: |z| < 50cm, 5tracks 0.84 Eff (geom, det., tracking, match) 0.37 0.05 jj Jet Eff (jet quality cuts) 0.99 0.01 f bg Frac background (Pt > 4 GeV) Pt dependent f HF Frac heavy flavor (Pt > 4 GeV) Pt dependent Efficiencies. [0.37 0.05] JES Definitions l Required identically 2 jets Pt(jet 3, uncor) < 8 OR third jet doesnt pass jet QC l One jet contains muon, the other doesnt. | | > 2.84 l Imbalance variable: l Independent variable: Jet energy scale for -tagged jets l -tagged jets also have neutrinos offset -- correction needed l Imbalance in events with 2 jets (one with, one without ) find 3.8% offset, not strongly p t dependent for p t in (75, 250GeV) l Scale energies of -tagged jets by factor l Order-randomized imbalance used to get resolution STD JES 5.3 gives a 3.8% offset for -tagged jets. It is independent of Pt ( GeV). Maybe higher above that. Need to rebin and revisit the idea that the muon Pt may be mis- measured. Same plot when scaling the -tagged jet energies by 3.8%. Energy Resolution resolution Neutrinos in -tagged jet resolution worse than for jets without take rms of order randomized imbalance l Parameterize, Fit (fig. (a)) Subtract (in quadrature) resolution for jets without obtain resolution for -tagged jets (fig. (b) l Fit: N = 7.7 4.1 S = 1.9 0.1 C = 0.0 0.1 l Resolution parameterization used in unsmearing Fitting Functions VariableValueError N1N k1k N2N k2k VariableValueError N9.56 10 6 Extraction of Correction Factors exponential normal Point by Point Unsmearing Factors Exponential normal Unsmearing Error small ~5% for Pt > 100 GeV HF fraction of -tagged jet sample l Sample of jets with -tagged jets contains jets with from non-HF sources (e.g. , K decays) l Use Pythia with standard D detector simulation to find HF fraction of jets tagged with muons vs (true) p t l Fit with A + B e -Pt/C A = plateau, B = zero C = turnon l Pythia using standard D MC. l NLO uses NLO++ (CTEQ6L) From Pythia, find fraction of jets tagged with muons (HF only). Multiply NLO cross-section by Pythia muon-fraction. This is effectively the NLO k factor. Conc l D Note and Conference note to EB025 l Residual small bug in code (should have only a few percent effect). l JES error must be reduced to use this before setting limits on new physics.