View
216
Download
0
Embed Size (px)
Citation preview
September 17-20, 2003. Kenichi Hatakeyama 1
Soft Double Pomeron Exchange in CDF Run I
Kenichi HatakeyamaThe Rockefeller Universityfor the CDF Collaboration
Small-x and Diffraction 2003Fermilab, Illinois, USA
September 17-20, 2003. Kenichi Hatakeyama 3
Main Issue in Hadronic Diffraction :results from single diffractive (SD) dijet production
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.
~10
Factorization Breakdown
CDF Collaboration, Phys. Rev. Lett. 84, 5043-5048 (2000).
September 17-20, 2003. Kenichi Hatakeyama 4
Dijet Production in DPE
Dijet production by double pomeron exchange was studied by CDF.
R[DPE/SD] is larger than R[SD/ND] by a factor of about 5.
CDF Collaboration, Phys. Rev. Lett. 85, 4215-4220 (2000).
The formation of the 2ndgap is not as suppressed
as the 1st gap.
Extract diffractive structure function fromR[DPE/SD] and compare it with expectations from HERA results.
September 17-20, 2003. Kenichi Hatakeyama 5
Diffractive Structure Functionmeasured using DPE dijet events
The diffractive structure function measured using DPE dijets is approximately equal to expectations from HERA!
Factorizationholds?
SDDPE
R from
NDSD
R from
September 17-20, 2003. Kenichi Hatakeyama 6
1/ σσ totSD 2TeV.s at
Unitarity problem :Soft Diffraction :Inclusive (Soft) SD Results
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 √s-dependence of σSD.
Is the formation of the second gap suppressed?
Tevatrondata
StudyDPE
Similar results were obtainedfor double diffraction as well.
ξs).(s'σξ)(t,fdtdξ
σdpIPIP/p
SD2
Renormalization
September 17-20, 2003. Kenichi Hatakeyama 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).
GeV. 1800s at 0.21σ
σ
SD
DPE
GeV. 1800s at 0.041σ
σ
SD
DPE
GeV. 1800s at 0.36σ
σ
SD
DPE
,s'(0)βκeπ4)β(t
dtdtdξdξ
σd ε22
P
2
p,pi
Δy1)α(ti
pppp
DPE4
gap
ii
,s'(0)βκ)t,(ξ)ft,(ξfdtdtdξdξ
σd ε22ppIP/ppppIP/
pppp
DPE4
=
tly.independen edrenormaliz are f and f Both pIP/IP/p
κ=g/β(0).
g:triple-Pomeron coupling,
coupling, )pp(IP:β(t)
flux, Pomeron:f )pIP/p(
momentum fractional:ξ )pp(
),pp( of loss
pp t,ξ
pp t,ξ
September 17-20, 2003. Kenichi Hatakeyama 8
Analysis Strategy Use events triggered on a leading
antiproton.
ξpbar is measured by Roman Pots : ξpbar
RPS.
Measure ξp (ξpbar) from BBC and calorimeters : ξp
X (ξpbarX).
Calibrate ξX by comparing ξpbarRPS
and ξpbarX.
Plot ξpX distribution and look for a
DPE signal expected in the small ξp
X region.
September 17-20, 2003. Kenichi Hatakeyama 9
Reconstruction of ξpX
Calorimeters : use ET and η of towers above noise level.
BBC : use hits in BBC scintillation arrays. pT is chosen to follow the
“known” pT spectrum :
Use calorimeter towers andBBC hits to reconstruct ξp :
.s
)ηexp(Eξ i iiT,X
p
./1.27)p(1pdpdσ 0.3)]35.8/ln(M/[4
TTT
Calorimeters
BBC
September 17-20, 2003. Kenichi Hatakeyama 10
Calibration of ξX
.)P2
P1ξexp(
P2P1ξ
0.5P3exp)f(
ξX distribution in every ξRPS bin is fitted toP1 : PeakP2 : Width
P2/P1 = 0.57(ξX resolution is ~60%.)
ξX = ξRPS,(ξX is calibrated so that
ξX = ξRPS.)
September 17-20, 2003. Kenichi Hatakeyama 11
ξpX Distribution
The input ξp distribution in DPE MC is 1/ξp
1+ε (ε = 0.104 is obtained from p±p/π±p/K±p total cross sections).
The DPE and SD MC distributions are independently normalized to the data distribution.
The measured ξpX
distribution is in agreement with the DPE+SD MC distribution.
September 17-20, 2003. Kenichi Hatakeyama 12
DPE Fraction in SD Events0.095,ξ0.035 p 0.02ξp
)0.011(syst)0.001(stat0.195SD(incl)
DPER
GeV. 1800s at
GeV. 630s at )0.012(syst)0.001(stat0.168
SD(incl)DPE
R
R[DPE/SD(incl)]Source @ 1800 GeV @ 630 GeV
Data 0.195±0.001±0.011
0.168±0.001±0.012
Regge + factorization 0.36 0.25
Flux Renormalization 0.041 0.041
Pgap Renormalization 0.21 0.17In agreement with the renormalized gap predictions!
September 17-20, 2003. Kenichi Hatakeyama 13
Soft Diffraction :Summary
σ (
mb
)G
ap
Fr
act
ion
Good Agreement withRenormalized Gap Predictions!
(GeV) s (GeV) s
(GeV) s (GeV) s'
SD DD
DPESDD
September 17-20, 2003. Kenichi Hatakeyama 14
Conclusions The measured ξp
X distribution exhibits ~1/ξ1+ε behavior (ε = 0.104).
The measured DPE fraction in SD is :
for 0.035 <ξpbar< 0.095 and ξp< 0.02 at √s = 1800 GeV.
in agreement with the renormalized gap prediction.
In events with a rapidity gap,the formation of a second gap is
“unsuppressed”!
)0.011(syst)0.001(stat0.195SD(incl)
DPER