New CDF Results on Diffraction Talk given in Moriond QCD 2006 by K. - PowerPoint PPT Presentation

New CDF Results on Diffraction Talk given in Moriond QCD 2006 by K. Terashi The Rockefeller University Presented by Rainer Wallny, UCLA on behalf of the CDF Collaboration LISHEP 2006 Workshop on Collider Physics Rio de Janeiro, Brazil, 2-7 April 2006 1

p-p Interactions Diffractive: Non-diffractive: vacuum exchange color exchange Protons retain their Protons acquire color and break apart quantum numbers GOAL : understand the nature of colorless exchange 2

Outline Diffractive Structure Function ➢ Ratio SD/ND dijets vs x Bjorken ➢ Q 2 dependence of SD/ND ratio ➢ Q 2 dependence of t in SD dijets Exclusive Production ➢ Exclusive di-jet ➔ Inclusive+Exclusive di-jet Monte Carlo ➔ Heavy flavor jet fraction ➢ Exclusive di-electron and di-photon Summary 3

Diffractive Structure Function Use high p T jets as a probe ➔ Hard Diffraction Diffractive Di-Jets : D ⊗    p p   p X  ≈ F jj ⊗ F jj  ab  jj  D = F jj D  ,t , x Bj , Q 2  F jj Diffractive Structure Function D Pomeron Experimental Determination of F jj  = P Pomeron / P proton  jj  SD  D  x Bj , Q 2  F jj R ( x Bj ) of = (LO QCD)  jj  ND  2  F jj  x Bj , Q Data Known Proton PDF 4

Ratio SD/ND Dijets vs x Bjorken ➢ agreement with Run I result ➢ no  dependence in 0.03<  <0.09 ➔ confirms Run I results 5

Q 2 Dependence of SD/ND Ratio No appreciable Q 2 dependence Pomeron evolves ➔ in region 100< Q 2 <10000 GeV 2 similarly to proton 6

Q 2 Dependence of t in SD Dijets Slope at t = 0 is independent of Q 2 7

Exclusive Production Exclusive  ,  c Exclusive Dijet  ,  c , ... gg → gg, qqg, ... gg →  , gg →  c , ... gg → qq J Z =0 suppressed clean signatures Measure exclusive dijet and  cross sections to calibrate predictions for exclusive Higgs production at the LHC 8

Search for Exclusive Dijets Strategy ➢ Select inclusive DPE dijets : p + p  p + X ( ≥ 2jets, ...) + gap ➢ Reconstruct dijet mass fraction : R jj = M jj not detected M X M X ➢ Look for excess in data over inclusive DPE dijet MC (POMWIG) Excess of events in data observed at high R jj Is this exclusive signal? 9

Inclusive+Exclusive Dijet Monte Carlo vs Data ExHuME (KMR) : gg → gg Exclusive DPE (in DPEMC) : IP IP → 2 jets The excess at high R jj is well described by the two exclusive dijet production models 10

Heavy Flavor Jet Fraction vs R jj Exclusive gg → qq Jz=0 suppression is expected Use b/c-quark Jet Data Look for suppression of b/c -quark illustration jet fraction in the high R jj region - many exp. systematics cancel in ratio - b/c -quarks identified event-by-event Ratio of b / c -jets to all jets (normalized to the mean in R jj <0.4) ⇩ Decreasing trend observed at high R jj 11

Comparing Inclusive Jet and Heavy Flavor Jet Results ➔ F 1 ➔ F 2 The two results are consistent with each other 12

Exclusive ee Candidates E T (1) = 6.1 GeV Good control sample E T (2) = 6.0 GeV for pp → p  p search 10 candidate events observed no background estimate yet 9 ± 3 events predicted by LPAIR Monte Carlo 13

Exclusive  Candidates E T (1) = 6.8 GeV E T (2) = 5.9 GeV 3 candidate events observed no background estimate yet 1 +3 events predicted by -1 ExHuME Monte Carlo (based on Khoze, Martin, Ryskin, Ref: Eur. Phys. J. C38, 475-482, 2005) 14

Summary D : Diffractive Structure Function F ➢ Confirmed and extended Run I results using single diffractive dijets  Pomeron evolves like proton? ✔ Q 2 dependence of F jj D ✔ Slope at t = 0 is independent of Q 2 Exclusive Production : ➢ Observed excess events in data at high R jj , being consistent with the presence of exclusive dijets ➢ Heavy flavor jet yield relative to inclusive jets appears to be decreased at high R jj  manifestation of Jz = 0 suppression? ➢ Observed events which appear to be consistent with pp → p  p ✔ pp → peep : nice cross check for di-photon ➢ Exclusive  and dijet cross sections measured soon Important inputs to pp → pHp at LHC 15

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Title:/home/cdf/tml/cdfii_thumb_logo.e Creator:GIMP PostScript file plugin V 1. CreationDate:Tue May 18 09:53:04 2004 LanguageLevel:2 Run II Detectors 17

DPE Dijet Events : R jj = M jj /M X (CAL) CDF ⊕ H1-fit2 D ~1/  ( f g =0.54, f q =0.46) F jj on one side, H1-fit2 on the other side D ~1/  ( f g =0.54, f q =0.46) CDF F jj on both sides H1-fit2 H1-fit2 on both sides 18

HF-Jet Fraction vs R jj All systematic uncertainties Normalized to the mean in R jj <0.4 added in quadrature 19

Jet Pseudorapidity Cuts 20

Dijet Mass Fraction : 3 rd Jet Veto + (A) Normalizations fixed to the ones obtained in the fits to 3 rd jet veto only Distributions scaled using #events falling into (A) Fit POMWIG + ExHuME/DPEMC to data 21

Dijet Mass Fraction : 3 rd Jet Veto + (B) Normalizations fixed to the ones obtained in the fits to 3 rd jet veto only Distributions scaled using #events falling into (B) 22

HF Fractions from SecVtx Tag Mass CDF Run II Preliminary CDF Run II Preliminary # of Tagged Jets # of Tagged Jets DPE data (SVT) DPE data (SVT) 200 200 b-jet b+c-jet c-jet others 150 150 others 3-Component Fit : 2-Component Fit : 100 100 b-jet : 0.49 0.07 ± b+c-jet : 0.91 0.05 ± c-jet : 0.44 0.09 ± others : 0.09 0.04 ± others : 0.07 0.04 ± 50 50 0 0 0 1 2 3 4 5 6 0 1 2 3 4 5 6 SecVtx Mass (GeV) SecVtx Mass (GeV) 3