inclusive double-pomeron exchange at the fermilab collider
DESCRIPTION
CDF Paper Seminar October 23, 2003. Inclusive Double-Pomeron Exchange at the Fermilab Collider. Authors : M.E. Convery, K. Goulianos, K. Hatakeyama The Rockefeller University Godparents : Andrey Korytov, Giorgio Bellettini, Mario Martinez-Perez PRL Draft : CDF Note 6568. - PowerPoint PPT PresentationTRANSCRIPT
1
Inclusive Double-Pomeron Exchange at the Fermilab Collider
Authors : M.E. Convery, K. Goulianos, K. Hatakeyama
The Rockefeller University
Godparents : Andrey Korytov, Giorgio Bellettini, Mario Martinez-Perez
PRL Draft : CDF Note 6568
CDF Paper SeminarOctober 23, 2003.
pp
October 23, 2003. Kenichi Hatakeyama 2
History of the Analysis Analysis blessed on May 2, 2002 and May 16,
2003.
PRL Draft : CDF Note 6568Comments from University of Toronto group UC Davis group University of Illinois group Universita di Padova group
Main Analysis Document : CDF Note 5865 Analysis Web Page :
http://www-cdf.fnal.gov/internal/people/links/KenichiHatakeyama/idpe.html
Many Thanks!
October 23, 2003. Kenichi Hatakeyama 3
High Energy Particle Diffraction
Several of our collaborators have expressed an unfamiliarity with diffractive physics.
This talk will start with a brief introduction to diffraction at CDF.
Details may be found in textbooks such as this.
Also, “Diffractive interactions of hadrons at high energies”,K. Goulianos, Phys. Rep. 101, 169 (1983)would be helpful for understanding the basics of soft hadron-hadron diffraction.
V. Barone, E. Predazzi,Springer Press, 2002.
October 23, 2003. Kenichi Hatakeyama 4
Introduction
Shaded Area :Region of Particle
Production
Diffraction in high energy hadron physics refers to a reaction in which no quantum numbers are exchanged betweencolliding particles.
October 23, 2003. Kenichi Hatakeyama 5
CDF Publications on Diffraction in Run 1
Single Diffractive(SD)
Double Diffractive (DD)
Double Pomeron Exchange (DPE)
Single+Double Diffractive (SDD)
PRD 50 (1994) 5535
PRL 87 (2001) 141802
This paper!PRL 91 (2003) 011802
Single Diffractive (SD) Jet-Gap-Jet Double Pomeron Exchange (DPE)
W : PRL 78 (1997) 2698Dijet : PRL 79 (1997) 2638b-quark: PRL 84 (2000) 232J/ψ : PRL 87 (2001) 241802
Dijets + Roman PotsPRL 84 (2000) 5043PRL 88 (2002) 151802
PRL 74 (1995) 855PRL 80 (1998) 1156PRL 81 (1998) 5278
Dijet : PRL 85 (2000) 4217
Soft Diffraction
Hard Diffraction (diffraction +hard scattering)
October 23, 2003. Kenichi Hatakeyama 6
What did we learn from hard diffraction?
Main issue in hadronic diffraction :
Do hard diffraction processes obey QCD factorization? (Are the diffractive parton distribution functions universal?)
This question can be addressed by comparing the functions extracted from different processes.
For SD dijet production,
.ˆ
),,()(ˆ ,
//td
dtxfxf
tdtdpddxdx
d jjab
bap
Dpbppa
pp
SD
ically.quasielast scattered is which antiproton the inpartons for ondistributi yprobabilit:/
Dpbf
ND
SD
October 23, 2003. Kenichi Hatakeyama 7
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).
Next Q : How is it broken?
October 23, 2003. Kenichi Hatakeyama 8
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.
October 23, 2003. Kenichi Hatakeyama 9
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
October 23, 2003. Kenichi Hatakeyama 10
Soft Diffraction : Regge Theory
g(0)/β(0)κ
coupling IPtriple: g(t)
coupling )pp(IP: β(t)
trajectory Pomeron: (t)α
factor flux Pomeron:)(t,f
IP
IP/p
Single Diffractive Cross SectionΔy
2
es
)s'(Mp
Δpξ
)(s'
ε
0
ξ)(t,
(t)2α12
SD2
σ
ss'
β(0)g(t)
f
ξ16π
(t)βdtd
σd
totpIP
IP/p
IP
Total Cross Section1-(0)
0
2tot
IP
ss
(0)β)(σ
s
176 (1996) 389 PLB in 0.104ε
α'tε1(t)αIP
σto
t
(mb
)
√s (GeV)
October 23, 2003. Kenichi Hatakeyama 11
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
RenormalizationK. Goulianos, PLB 353, 379 (1995).
October 23, 2003. Kenichi Hatakeyama 12
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
October 23, 2003. Kenichi Hatakeyama 13
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.
October 23, 2003. Kenichi Hatakeyama 14
Roman PotSpectrometer
Roman Pots detectrecoil antiprotons
October 23, 2003. Kenichi Hatakeyama 15
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 :
•Cannot reconstruct ξp by RPS.•Use calorimeter towers and BBC 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
(J. Collins, hep-ex/9705393)
The CAL+BBC method allowed us to accessall the way down to the kinematic limit.
October 23, 2003. Kenichi Hatakeyama 16
Data Sample and Event Selection
Roman Pot triggered data collected in 1800 GeV low luminosity runs during Run 1C (<Linst> ~ 0.2 x 1030 cm-2s-1).
Overlap event (containing SD + additional ND collisions which kill the rapidity gap signal ) rate is low (~4% ~0.5% after the cuts shown below).
Selection Cut Number of EventsTotal 1200779Number of vertices ≤ 1 1123407|zvtx| ≤ 60 cm (if there is one) 10588761 MIP in the RP trigger counters 9717491 or 2 reconstructed tracks in RPS 763268
660240West BBC multiplicity ≤ 6 568478
2pp GeV 1.0|t| .095,ξ.035
October 23, 2003. Kenichi Hatakeyama 17
Monte Carlo Event Generation : MBR(CDF Note 0256, 0675, 5371. PRD 50 (1994) 5535, 5550.)
SD and DPE event generationMBR min-bias MC: Specially designed to reproduce soft-interaction results
from low-energy experiments Used to determine CDF total, SD and DD cross sections
[PRL 50 (1994) 5535, 5550, PRL 87 (2001) 141802.]
Detector simulationCalorimeters: not well calibrated for low pT particles. Convert the generated particle pT to the calorimeter ET
using calibrations determined specifically for low-pT particles.
BBC: assume that all charged particles will trigger the BBCs.
)ss' at collisions pp as decayed are clusters mass (DPE Convery
M.E. by developed events DPE simulate to MBR for code New
pp
October 23, 2003. Kenichi Hatakeyama 18
Calibration of ξX
.)exp(0.5P3exp)f(P2
P1ξ
P2
P1ξ
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.)
October 23, 2003. Kenichi Hatakeyama 19
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.
October 23, 2003. Kenichi Hatakeyama 20
ξpX Distribution
The ξp distribution on the previous page shows “number of events per Δlogξ=0.1”;
Multiply each bin by 1/ξ to show dN/dξ.
A diffractive peak of 3 orders of magnitude is observed!
ξ.dξdN
dlnξdN
0.1Δlogξevents of#
October 23, 2003. Kenichi Hatakeyama 21
SD(incl)
DPER Fraction Event DPE
)0.001(stat0.2020.04)1.04(/F568478119406
R resolSD(incl)
DPE
)0.001(stat0.194SD(incl)
DPER
Corrections to R[DPE/SD(incl)] : ξp
X resolution : According to MC, more events with
ξp>0.02 seem to fall into ξpX<0.02 than
events with ξp<0.02 fall into ξpX>0.02.
R[DPE/SD(incl)] is corrected by Fresol=1.04±0.04
Low ξpbarX enhancement:
3~4 % of events have very low ξpbarX
values although those events have 0.035< ξpbar
RPS <0.095. MC shows a similar effect, but not as
pronounced as in data. Obtain R[DPE/SD(incl)] with/without
ξpbarX<0.003 cut, and take the average.
0.02ξ ,GeV 1|t| 0.095,ξ0.035 for Xp
2pp
October 23, 2003. Kenichi Hatakeyama 22
Source Estimator Uncertaintyξp
X calibration Change ξpX by 10 % 0.003 (2%)
ξpX resolution Whole correction 0.008 (4%)
Low ξpbarX
enhancementHalf of the variation 0.008 (4%)
Total 0.012 (6%)
0.02.ξ and GeV 1|t|0.095,ξ0.035 for
)0.012(syst)0.001(stat0.194SD(incl)
DPER
Xp
2pp
dcont'R Fraction Event DPE SD(incl)
DPE
Systematic Uncertainties
The measured fraction is in agreement with the predictionfrom the renormalized gap probability model (0.21±0.02)!
October 23, 2003. Kenichi Hatakeyama 23
Source R[DPE/SD(incl)]
Data 0.195±0.001±0.010
Regge 0.36±0.04
Flux Renormalization 0.041±0.004
Pgap Renormalization 0.21±0.02
0.02ξ ,GeV 1|t| 0.095,ξ0.035 p2
pp
)0.012(syst)0.001(stat0.194RSD(incl)
DPE
In agreement with the renormalized gap predictions!
dcont'R Fraction Event DPE SD(incl)
DPE
Comparisons with phenomenological models
October 23, 2003. Kenichi Hatakeyama 24
Proton Dissociation EventsOur “DPE” signal actually consists of two classes of events; Events in which both the proton and antiproton escape
intact from the collision typically called “DPE”. Events in which the antiproton escapes intact from the
collision, while the proton dissociates into a small mass cluster Y (MY
2 <~8 GeV2) proton dissociation events.
Particles in Y have rapidity up to y=7.5.
In 35% of events (“A”), east BBC covers up to η=5.9,
MY2 < e 7.5 - 5.9 = 5 GeV2.
In 65% of events (“B”), east BBC covers up to η=5.2,
MY2 < e 7.5 - 5.2 = 10 GeV2.
R[DPE/SD(incl)] is larger in “B” than in “A” by 6%.
Weighted average : 8 GeV2
22minY,
2Y 1.5GeV~M const.,~Mln/ dd
The contribution of proton dissociation events
with 1.5<MY2<8GeV2 to R[DPE/SD(incl)] is ~15%.
All the particles in Y go beyond BBC so that the event is indistinguishable
from “DPE” events.
DPE
Proton dissociation event
October 23, 2003. Kenichi Hatakeyama 25
Soft Diffraction :Summary
σ (
mb)
Gap F
ract
ion
Good Agreement withRenormalized Gap Predictions!
(GeV) s (GeV) s
(GeV) s (GeV) s'
SD DD
DPESDD
October 23, 2003. Kenichi Hatakeyama 26
Summary We have observed double pomeron exchange events
in an inclusive single diffractive event sample. 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, |tpbar|<1 GeV2, ξpX< 0.02 and MY
2<~8GeV2at √s = 1800 GeV,
in agreement with the renormalized gap prediction.In events with a rapidity gap,
the formation of a second gap is “unsuppressed”!
)0.012(syst)0.001(stat0.194RSD(incl)
DPE
Consistent with results from hard diffraction
Universality of the rapidity gap formation
October 23, 2003. Kenichi Hatakeyama 27
SDDPE
R from
NDSD
R from
Summary +
The diffractive structure function measured using DPE dijets is approximately equal to expectations from HERA!
Universality of rapidity gap formation across soft and harddiffraction processes.
Events with multiple rapidity gaps can be used to eliminatethe “suppression” factor… Facilitate QCD calculation of hard diffraction.
October 23, 2003. Kenichi Hatakeyama 28
Backups
October 23, 2003. Kenichi Hatakeyama 29
Regge Theory & Factorization
g(0)/β(0)κ
coupling IPtriple: g(t)
coupling )pp(IP: β(t)
trajectory Pomeron: (t)α
factor flux Pomeron:)(t,f
IP
IP/p
Single Diffractive Cross Section
Δy2
es
)s'(Mp
Δpξ
)(s'
ε
0
ξ)(t,
(t)2α12
SD2
σ
ss'
β(0)g(t)
f
ξ16π
(t)βdtd
σd
totpIP
IP/p
IP
Total & EL Cross Sections
1-(0)
0
2tot
IP
ss
(0)β)(σ
s
176 (1996) 389 PLB in 0.104ε
α'tε1(t)αIP
1]-(t)2[α
0
4EL
IP
ss
16π(t)β
dt
(s)dσ
October 23, 2003. Kenichi Hatakeyama 30
Unitarity ProblemSingle Diffractive Cross Section
ε12
2ε
2SD
2ε1SD
)(Ms
dM
dσ)(
ξ1
dξ
dσ s2Mξ
εξs
Total Cross Sectionε
tot sσ
ε
tot
SD sσ
σ
[ε=0.104 in PLB 389 (1996) 176]
The ratio σDPE/σSD reaches unity at √s~2 TeV.
In data, s2ε in dσSD/dM2 1
October 23, 2003. Kenichi Hatakeyama 31
Soft Single Diffraction Results
KG&JM, PRD 59 (1999) 114017 KG, PLB 358 (1995)379
Differential cross section agrees with Regge predictions (left) Normalization is suppressed by flux factor integral (right)
dσSD/dM2 σSDtot versus √s
October 23, 2003. Kenichi Hatakeyama 32
RenormalizationSingle Diffractive Cross Section
ε12
2ε
2SD
2ε1SD
)(Ms
dM
dσ)(
ξ1
dξ
dσ s2Mξ
εξs
In data, s2ε 1
Renormalization
K. Goulianos, Phys. Lett. B 358 (1995) 379
2ε0.1
/sM 2ε1ren sdξξ
11/N
20
ε12ε12
2ε
ren2SD
)(M1
)(Ms
NdM
dσ
October 23, 2003. Kenichi Hatakeyama 33
Soft Double Diffraction Results
CDF, Phys. Rev. Lett 87 (2001) 141802
Differential cross section agrees with Regge predictions (left) Normalization is suppressed by flux factor integral (right)
dσDD/dΔη0 σDDtot versus √s
')'( )()( yyt
c
DD eeydydtd
d
0
4
0 2
23
October 23, 2003. Kenichi Hatakeyama 34
Past Experimental Results : UA8 Collaboration
NLB 514 (1998) 3, PLB 481 (2000) 177, EPJC 25 (2002) 361.
Extracted σIPIPtot using FIP/p(ξ,t) from their
SD analysis.
The extracted σIPIPtot shows an
enhancement at low MX. They attributed it to the glueball
production......
Note : If the standard ε~0.1 is used, the enhancement is reduced significantly. But, the extracted σIPIP
tot is overall higher than the expectation.
GeV 630s at collider SpSpCERN the at events DPE and SD studied ionCollaborat UA8
)(s'σ)t,(ξF)t,(ξFdtdξdtdξ
σd totIPIPppIP/ppppIP/
pppp
DPE4
Consistent with our results
October 23, 2003. Kenichi Hatakeyama 35
Beam-Beam Counters
In 35% of events(“A”),
Red : Dead ChannelsLight blue : Channels
used to reconstruct ξX
In 65% of events (“B”),
East BBC
East BBC
West BBC
West BBC
October 23, 2003. Kenichi Hatakeyama 36
Reconstruction of ξpX : BBC
BBC (ξpBBC) : use hits in BBC scintillation
arrays use only inner 3 (shaded) layers (the most-
outer layer overlaps with the forward cal). pT is chosen to follow the “known” pT spectrum
η is chosen randomly within the η range of the BBC counter which has a hit.
.ξξs
)ηexp(Eξ CAL
pBBCp
i iiT,Xp
Use calorimeter towers and BBC hits to reconstruct ξX,
).0.065s(M ,/1.27)p(1pdpdσ 0.3)]35.8/ln(M/[4
TTT
OK. is 0.065sM setting soM, with slowly very changes spectrum p The T
October 23, 2003. Kenichi Hatakeyama 37
Reconstruction of ξpX :Calorimeter
Calorimeter (ξpCAL) : use ET and η of towers above the noise level
ξpCAL has to be corrected for
Calorimeter non-linearity at low ET region
Particles below the applied ET threshold
The correction factor for ξCAL is obtained so that ξX(median):ξRPS=1:1.
.ξξs
)ηexp(Eξ CAL
pBBCp
i iiT,Xp
2.7f ,fed)(uncorrectξξξ corrcorrCALp
BBCp
Xp
October 23, 2003. Kenichi Hatakeyama 38
ξX Calibration :ξpbar
X distributions in 9 ξpbarRPS intervals
ξX distribution inevery ξRPS bin isfitted to
.)exp(0.5P3exp)f(P2
P1ξ
P2
P1ξ
P1 : Peak, P2 : Width
•ξX(median) = 0.94 ξRPS
calibrated later to obtain ξX(median)=ξRPS
•P2/P1 = 0.57 (ξX resolution is ~60%.)
October 23, 2003. Kenichi Hatakeyama 39
ξpbarX Distribution
We calibrated ξX so that ξX(median) : ξRPS becomes 1 : 1.
The choice of P1/median/mean does NOT make adifference in R[DPE/SD(incl)], since the choice is takeninto account by the ξX resolution correction, Fresol.
October 23, 2003. Kenichi Hatakeyama 40
BBC Multiplicities in MC
The peak at EBBC=0 in data distributions is due to DPE events. The MBR SD MC whose dN/dη is already checked in PRD 50
(1994) 5535, shows much lower multiplicities in the east BBC. The higher BBC multiplicities in data are presumably due to
“splashes” which are hard to simulate. In SD MBR, for east BBC hits, don’t use the information of particles generated by MBR but simulate east BBC hits according to the data east BBC multiplicities.
“A” “B”
October 23, 2003. Kenichi Hatakeyama 41
BBC Contribution to ξX
(A) (B)
October 23, 2003. Kenichi Hatakeyama 42
ξpX resolution correction
Generate ξ by using dσ/dξ from F. Abe et al., PRD 50 (1994)
5535. K. Goulianos & J. Montanha,
PRD 59 (1999) 114017.
Smear ξ according to the form:
- P2/P1 = 0.57, P1 = 0.67ξ (P1 = 0.67xmedian when
P2/P1=0.57)
The number of events with ξ<0.02 increases about 4% after the smearing.
.)exp(0.5P3exp)f(P2
P1ξ
P2
P1ξ
Fresol=1.04±0.04