predictions of soft processes at the lhc implemented in pythia8 konstantin goulianos* the...
DESCRIPTION
INTRODUCTION low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 3 This is an adaptation of the MBR (Minimum Bias Rockefeller) simulation RENORM to PYTHIA8. successfully tested at Fermilab fixed target and collider experiments. RENORM predictions are based on a parton model approach, in which diffraction is derived from inclusive PDFs and color factors. Gap Cross Sections: Gap cross sections vs gap width: Absolute normalization! Hadronization of dissociated proton: Implemented by introducing a (non-perturbative) “quark string” and tuning it to reproduce the MBR multiplicity and p T distributions. dN/d , p T, and particle ID (new in this implementation; the original MBR produced only ± and 0 ) Unique unitarization procedure based on a saturated exchange. Total Cross section: based on a saturated Froissart bound leading to a ln 2 s dependence. Immune to eikonaalization models that plague the field!TRANSCRIPT
Predictions of Soft Processes at the LHC Implemented in PYTHIA8
Konstantin Goulianos*
The Rockefeller University
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low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 1
* with:Robert Ciesielski
CONTENTS
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 2
INTRODUCTION
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 3
This is an adaptation of the MBR (Minimum Bias Rockefeller) simulation RENORM to PYTHIA8. successfully tested at Fermilab fixed target and collider experiments.
RENORM predictions are based on a parton model approach, in which diffraction is derived from inclusive PDFs and color factors.
Gap Cross Sections: Gap cross sections vs gap width:
Absolute normalization! Hadronization of dissociated proton:
Implemented by introducing a (non-perturbative) “quark string” and tuning it to reproduce the MBR multiplicity and pT distributions.
dN/d, pT, and particle ID (new in this implementation; the original MBR produced only ± and 0)
Unique unitarization procedure based on a saturated exchange. Total Cross section: based on a saturated Froissart bound leading to a ln2s
dependence. Immune to eikonaalization models that plague the field!
STUDIES OF DIFFRACTION IN QCD Diffractive Colorless vacuum exchange large-gap signature
Non-diffractive color-exchange gaps exponentially suppressed
POMERON
Goal: probe the QCD nature of the diffractive exchange
rapidity gapIncident hadrons acquire colorand break upart
CONFINEMENT
Incident hadrons retain their quantum numbersremaining colorless
p p p p
p
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 4
DEFINITIONS
MX
dN/d
,t
p’Rap-gap=-ln
0seEΣξ
iηtower-iT
all1iCAL
sM2
Xξ1- Lx
ln s
22 M
1
dM
dσξ1
dξdσconstant
Δηddσ
0t
ln Mx2
ln ssince no radiation no price paid for increasingdiffractive gap size
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos
p pMX
p p’
SINGLE DIFFRACTION
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DIFFRACTION AT CDF
Single Diffraction orSingle Dissociation
Double Diffraction or Double Dissociation
Double Pom. Exchange orCentral Dissociation
Single + DoubleDiffraction (SDD)
SD DD DPE /CD SDD
Elastic scattering Total cross sectionT=Im fel (t=0)
OPTICALTHEOREM
gap
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos
JJ, b, J/W ppJJ…ee… exclusive
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Factor of ~8 (~5)suppression at √s = 1800 (540) GeV
diffractive x-section suppressed relative to Regge prediction as √s increases
see KG, PLB 358, 379 (1995)
1800
GeV
540
GeV
M,t
pp
p’
√s=22 GeV
RENORMALIZATION
Regge
FACTORIZATION BREAKING IN SOFT DIFFRACTION
CDF Question:
does factorization breaking affect t-distributions?
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 7
EDS-2011 Vietnam CDF Diffraction and Exclusive Production 8
DD at CDF
renormalized
gap probability x-section
EDS-2011 Vietnam CDF Diffraction and Exclusive Production 9
SDD at CDF
Excellent agreement between data and MBR (MinBiasRockefeller) MC
EDS-2011 Vietnam CDF Diffraction and Exclusive Production 10
CD (DPE) at CDF
Excellent agreement between data and MBR low and high masses are correctly implemented
Cross Sections
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 11
SD single diffraction (single dissociation) DD double dissociation (double diffraction) CD central dissociation (double pomeron exchange)
tot el
SD SD DD CD
Total, elastic, and inelastic x-sections
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 12
GeV2
Total, elastic, and inelastic x-sections versus √s
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 13
Difractive x-sections
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 14
1=0.9, 2=0.1, b1=4.6 GeV-2, b2=0.6 GeV-2, s′=s e-y, =0.17, 2(0)=0, s0=1 GeV2, 0=2.82 mb or 7.25 GeV-2
Difractive x-sections of √s
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 15
Supress x-sections at small gaps by a factor S using the error function with yS=2 for SD and DD, and y=y1+y2 =2 for CD (DPE).
SD and DD at 7 TeV
MBR vs PYTHIA8-4C
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 16
The differences between the PYTHIA8(4C) and MBR predictions are mainly due to the (1/M2)1+ behavior, with =1.104 in MBR vs 1,08 in PYTHIA8(4C).
CD (DPE) x-sections at 7 TeV versus (a) y=y1+y2 and (b) y1
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 17
Both figures are MBR predictions with a y=2 cut-off in the error function. The normalization is absolute with no model uncertainty other than that due to the
determination of the parameters in the formulas as determined from data
low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos
Thank you for your attention
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References in arXiv:1205.1446v1 [hep-ph]
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multiplicities