DPE and Exclusive Dijet Productions in Run II

We present results from studies of dijet events produced in Double Pomeron Exchange (DPE) in Run II. The events are selected from a sample of about 310 pb-1 of data collected with a dedicated diffractive trigger. We first measure cross sections of DPE dijet events for different minimum ET of the second leading jet. Then, we perform a search for events from exclusive dijet production pbar + p ---> pbar + Jet + Jet + p in the DPE dijet sample using a kinematic variable called dijet mass fraction, Rjj, defined as a dijet mass divided by the DPE system mass. The search is based on comparing the Rjj distribution shapes between the data and inclusive DPE dijet Monte Carlo predictions. We observe, for the first time, exclusively produced dijet events as a significant excess of data at high Rjj range. The cross sections of observed exclusive dijet events are measured using combinations of inclusive DPE and exclusive dijet Monte Carlo simulations. All blessed plots are combined in a PDF file.

Fractional Mometum Loss of (Anti)Proton Reconstrcuted from Calorimeters
DPE: XI_pbar(CAL)    [EPS][GIF]	DPE: XI_p(CAL)    [EPS][GIF]
SD: XI_pbar(CAL)    [EPS][GIF]	SD: XI_pbar(CAL)    [EPS][GIF]

BSC-1 vs MiniPlug Hit Multiplicities
Antiproton Side: RP+Jet5  [EPS][GIF]	Proton Side: RP+Jet5   [EPS][GIF]
Antiproton Side: Jet5     [EPS][GIF]	Proton Side: Jet5     [EPS][GIF]

Kinematic Distributions of DPE, SD and ND Dijets
Mean ET of Leading Two Jets [EPS][GIF]	Mean Pseudorapidity of Leading Two Jets  [EPS][GIF]
Azimuthal Angle Difference of Leading Two Jets [EPS][GIF]

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Data and POMWIG MC predictions are compared in the shapes of various kienamatic distributions. The following six Pomeron PDFs are used in the POMWIG MC.
 

CDF+H1	CDF Run I FjjD from DPE/SD dijets (FCDF on one side, H1-fit2 on the other side)
CDF	CDF Run I FjjD from SD/ND dijets (FCDF on both sides)
H1-fit2	H1 LO-fit2 to 1994 Large Rapidity Gap data (both sides)
H1-fit3	H1 NLO-fit3 to 1994 Large Rapidity Gap data (both sides)
ZEUS-LPS	ZEUS NLO-fit to 1997 LPS data (both sides)
ZEUS-Mx	Groys, Levy, Proskuryakov (GLP) NLO-fit to 1998-99 ZEUS Mx data (both sides)

FCDF is defined as F_jj^D ~ 1/beta (f_g=0.54, f_q=0.46) , where f_g(q) is the fraction of gluons (quarks) in the Pomeron.

Abstract

We have presented preliminary results on the search for exclusive dijet production using double Pomeron exchange (DPE) dijet data (see above). In the studies, we observe an excess of events in the data over backgrounds obtained from inclusive Monte Carlo and the excess is consistent with exclusive dijet Monte Carlo predictions in terms of kinematic distribution shapes. In the analyis presented here, we discuss an approach for extracting the exclusive dijet signal from the inclusive DPE dijet sample using heavy flavor quark jets. Preliminary results obtained from the data collected after the Fall 2004 shutdown are presented.