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Soft Double Pomeron Exchange in CDF Run I

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... from BBC and calorimeters : ?pX (?pbarX) ... Calorimeters : use ET and ? of towers ... Calorimeters. BBC. Calibration of ?X. ?X distribution in every ?RPS ... – PowerPoint PPT presentation

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Title: Soft Double Pomeron Exchange in CDF Run I


1
Soft Double Pomeron Exchange in CDF Run I
Small-x and Diffraction 2003 Fermilab, Illinois,
USA
  • Kenichi Hatakeyama
  • The Rockefeller University
  • for the CDF Collaboration

2
Introduction
Shaded Area Region of Particle Production
3
Main Issue in Hadronic Diffraction results from
single diffractive (SD) dijet production
CDF Collaboration, Phys. Rev. Lett. 84, 5043-5048
(2000).
  • The diffractive structure function measured using
    SD dijet events at the Tevatron is smaller than
    that at HERA by approximately an order of
    magnitude.
  • The discrepancy is generally attributed to
    additional color exchanges which spoil the
    diffractive rapidity gap.

Factorization Breakdown
4
Dijet Production in DPE
CDF Collaboration, Phys. Rev. Lett. 85, 4215-4220
(2000).
  • Dijet production by double pomeron exchange was
    studied by CDF.
  • RDPE/SD is larger than RSD/ND by a factor of
    about 5.

The formation of the 2nd gap is not as
suppressed as the 1st gap.
Extract diffractive structure function
from RDPE/SD and compare it with expectations
from HERA results.
5
Diffractive Structure Functionmeasured using DPE
dijet events
Factorization holds?
6
Soft Diffraction Inclusive (Soft) SD Results
Unitarity problem
  • The measured SD cross section is smaller than the
    Regge theory prediction by approximately an order
    of magnitude at the Tevatron energy.
  • Normalizing the integral of the pomeron flux
    (fIP/p) to unity yields the correct vs-dependence
    of sSD.

Tevatron data
Renormalization
Similar results were obtained for double
diffraction as well.
Study DPE
Is the formation of the second gap suppressed?
7
Inclusive (Soft) DPE Cross Section
  • Regge theory prediction factorization
  • Flux renorm. model
  • (both gaps are suppressed.) K. Goulianos, Phys.
    Lett. B 353, 379 (1995).
  • Gap probability (Pgap) renorm. model Pgap is
    renormalized.
  • (only one gap is suppressed.) K. Goulianos, e.g.
    hep-ph/0110240 (2001).

8
Analysis Strategy
  • Use events triggered on a leading antiproton.
  • ?pbar is measured by Roman Pots ?pbarRPS.
  • Measure ?p (?pbar) from BBC and calorimeters
    ?pX (?pbarX).
  • Calibrate ?X by comparing ?pbarRPS and ?pbarX.
  • Plot ?pX distribution and look for a DPE signal
    expected in the small ?pX region.

9
Reconstruction of ?pX
Calorimeters
Use calorimeter towers and BBC hits to
reconstruct ?p
  • Calorimeters use ET and ? of towers above noise
    level.
  • BBC use hits in BBC scintillation arrays.
  • pT is chosen to follow the known pT spectrum

BBC
10
Calibration of ?X
?X distribution in every ?RPS bin is fitted to
P1 Peak P2 Width
?X ?RPS, (?X is calibrated so that ?X ?RPS.)
P2/P1 0.57 (?X resolution is 60.)
11
?pX Distribution
  • The input ?p distribution in DPE MC is 1/?p1e (e
    0.104 is obtained from pp/pp/Kp total cross
    sections).
  • The DPE and SD MC distributions are independently
    normalized to the data distribution.
  • The measured ?pX distribution is in agreement
    with the DPESD MC distribution.

12
DPE Fraction in SD Events
RDPE/SD(incl) RDPE/SD(incl)
Source _at_ 1800 GeV _at_ 630 GeV
Data 0.1950.0010.011 0.1680.0010.012
Regge factorization 0.36 0.25
Flux Renormalization 0.041 0.041
Pgap Renormalization 0.21 0.17
In agreement with the renormalized gap
predictions!
13
Soft Diffraction Summary
SD
DD
s (mb)
DPE
SDD
Gap Fraction
14
Conclusions
  • The measured ?pX distribution exhibits 1/?1e
    behavior (e 0.104).
  • The measured DPE fraction in SD is
  • for 0.035 lt?pbarlt 0.095 and ?plt 0.02 at vs
    1800 GeV.
  • in agreement with the renormalized gap prediction.
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