QCD Results from the Tevatron

QCD Results from the TevatronKenichi HatakeyamaBaylor UniversityAspen Particle Physics ConferenceAspen Center of Physics January 17 - 23, 2010

January 18, 20102OutlineFermilab Tevatron, CDF and D0 DetectorsInclusive jets and dijetsPhotons W/Z+jetsSoft QCD and Exclusive ProductionSummary & Remarks

Only a small fraction of extensive QCD results from the Tevatron can be covered in 20 minutes. More results can be found on:http://www-cdf.fnal.gov/physics/new/qcd/QCD.htmlhttp://www-d0.fnal.gov/Run2Physics/WWW/results/qcd.htm

January 18, 20103Fermilab Tevatron>7 fb-1 delivered(Run I: 120 pb-1)Batavia, ILTevatronMain Injector

Worlds highest energy proton-antiproton collider

Most likely to run until FY2011January 18, 20104CDF and D

CDF & D running well and recording physics quality data with high efficiency (85-90 %)Both experiments have already collected > 6 fb-1 on tape Inclusive Jets & Dijetss, PDFs, Physics beyond the Standard ModelJanuary 18, 20106Jet Production at the TevatronTest pQCD at highest Q2.Unique sensitivity to new physicsCompositeness, new massive particles, extra dimensions, Constrain PDFs (especially gluons at high-x)Measure s

Hard ScatterPDFs

jetjet

underlyingevent

January 18, 20107Inclusive Jet Cross SectionMeasurements span over 8 order of magnitude in d2/dpTdyHighest pTjet > 600 GeV/c

pT (GeV/c)Phys. Rev. D 78, 052006 (2008) pT (GeV/c)Phys. Rev. Lett. 101, 062001 (2008)January 18, 20108Inclusive Jet Cross SectionBoth CDF and D0 measurements are in agreement with NLO predictionsBoth in favor of somewhat softer gluons at high-xExperimental uncertainties: smaller than PDF uncertaintiesDiscussions on the impact to PDF in a different talk

CTEQ6.5M PDFspT (GeV)see also, Inclusive jets with Kt, CDF, Phys. Rev. D 75, 092006.January 18, 20109Strong Coupling ConstantFrom 22 (out of 110) inclusive jet cross section data points at 50 < pT < 145 GeV/c

NLO + 2-loop threshold corrections MSTW2008NNLO PDFs

Extend HERA results to high pT

3.5-4.2% precisionPhys. Rev. D 80, 111107CDF results in Phys. Rev. Lett. 88, 042001January 18, 201010Dijet Mass SpectrumTest pQCD predictionsSensitive to new particles decaying into dijets: excited quarks, heavy gluons, techni-, etc

Dijets with jets |yjet| 20 GeV and || < 1.5

WHlbb search

Success of NLO QCD. Awaiting for differential measurements.

arXiv: 0909.1505January 18, 201038

UE in Jet and Drell-Yan ProductionJet production: Transverse region sensitive to UEHigh statistics jet sampleStudies in various dijet topologiesDY production:Transverse and toward regions (excluding lepton-pairs) sensitive to UECleaner environment (Z/* carries no color)Limited statistics

Leading jet / Z Direction

jet, , ZjetTransverse plane- PlaneUnderlying Event: everything except hard scatter

January 18, 201039UE in DY and Jet ProductionComparisons of three regionsAway region pT density goes up with lepton-pair pT, while the transverse and toward region pT densities are mostly flat with lepton-pair pT

Comparisons between jet and DY Similar trend in jet and DY events: UE universality?Tuned Pythia describe data reasonably well.

There are many more plots for UE in jet and Drell-Yan production correctedto hadron level: Very important for MC generator tuning/development

January 18, 201040

Double Parton using +3 JetsStudy interactions of two parton pairs in single proton:Insight to parton spatial distributions in the protonBackground to other process especially at high luminosities

Main backgroundsignalDP = j jj/eff

eff : effective interaction region(Large eff: partons more uniformly distributed)

4040January 18, 201041Double Parton Scattering

eff = 15.11.9 mb(consistent with previous CDF results.)Calculated for the pair that gives the minimum value of S:

D0 Note 5910

Jet #1 Direction

Toward

Transverse

Transverse

Away

-1

+1

2

0

Leading

Jet

Transverse

Region

Toward Region

Transverse

Region

Away Region

Away Region