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Experimental Tests of the BFKL Mechanism in Dijet Production at the Tevatron

This study investigates the BFKL dynamcis in dijet production at the Tevatron, focusing on inclusive dijet production and decorrelation in the azimuthal plane. Results show trends consistent with BFKL formalism qualitatively, but quantitative results do not align with LLA BFKL predictions. Data indicate potential sensitivity to BFKL dynamics. Ongoing studies include dijet cross section ratio analysis and exploration of Q2 distribution at 630 GeV and 1800 GeV.

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Experimental Tests of the BFKL Mechanism in Dijet Production at the Tevatron

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  1. Experimental Tests of the BFKL MechanismZarah CasilumState University of New York at Stony Brookfor the D0 Collaboration1997 Joint April APS/AAPT MeetingApril 18-21, 1997Washington, DC

  2. x1, kT1 x2, kT2 xn, kTn BFKL Dynamics at the Tevatron • Inclusive dijet production at large rapidities • Semi-hard region: For large x: • The BFKL formalism resums (asDh) to all orders in as (only leading logs) into the partonic cross section by using a multigluon amplitude

  3. The BFKL resummation results in an exponential growth of the partonic cross section • Contribution of real gluons leads to additional radiation between the two jets Decorrelation of the dijets in the azimuth Dijet decorrelation at large rapidities • Tevatron at a fixed cms energy (1.8 TeV) -At large Dh, PDF’s control dijet cross section -Difficult to see the growth of cross section with Dh -Look for evidence of additional radiation as Dh increases

  4. pt1f1 h1 Higher Order pt1f1 h1 LO pt2f2 h2 pt2f2 h2 • Measuring azimuthal decorrelation (cartoon analogy) Qualitative:broadening 1/N dN/dDf as Dh Quantitative:falling off <cos(p-Df)> as Dh

  5. The DO Detector • Hermetic coverage over large rapidity (|h| < 4.0) • Fine transverse segmentation (0.1 x 0.1 in Dh x Df) • Good jet energy response and resolution Side view of the DO Detector

  6. h=-3.5 h=3.5 Tagging Jet1 J1 X(Ji) Df Tagging Jet2 J2 Dh Event topology and Analysis variables • Jets: ET sums in 0.7 cone in h x f space • Single jet triggers: Inclusive: ET>12 Gev Forward: ET>12 GeV and |h|>1.6 • Multiple pp interactions and fake jets removed • Offline defines jets with ET>20 GeV , and |h|<3.5 • Rapidity ordering and tagging jets at extreme rapidities: (h1,f1),(h2,f2) • Require rapidity boost • Analysis variables: Dh = h1 - h2 and Df = f1 - f2

  7. Data Results: 1/N dN/dDf vs. Dh <cos(p-Df)> vs. Dh LLA

  8. 1800/630 GeV Dijet Cross Section Ratio at large Dh • Mueller and Navelet suggested a method to explore BFKL dynamics by describing s dependence(Nucl. Phys. B282 (1987) 727) • Fix x1, x2, Q2 and take the ratio of the cross sections at two different center of mass energies, sA and sB • Cancellation of the parton distribution functions, hence removing large source of theoretical error • By measuring R(1800,630) at the Tevatron, we can probe the perturbative BFKL dynamics and extract the effective coupling of the BFKL pomeron, aBFKL=1+12asln2/p (using as(Q2)=0.16)

  9. Q2 and x • Data set • 1800 GeV: integrated Lum = 1.5 nb-1 • 630 GeV: integrated Lum = 34 nb-1 • Offline cuts: similar cuts as the decorrelation analysis, except that |h|>2.0 • Q2 and x values: 1 bin: 400-1000GeV2 several bins: 0.06-0.25 630 GeV 1800 GeV

  10. Summary and Outlook • Decorrelation study -Qualitatively, data show trends consistent with BFKL -However, quantitative results do not agree with LLA BFKL but agree well with Herwig(V5.8, parton shower model, including ISR,FSR, interference terms) -LLA BFKL with improved kinematics will be available soon and NLL BFKL calculations are in progress • Dijet cross section ratio study -study under way -Very promising measurement;directly sensitive to BFKL dynamics

  11. Q2 Distribution 630 GeV 1800 GeV

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