1. Predictions of Soft Processes at the LHC Implemented in PYTHIA8 Konstantin Goulianos* The Rockefeller University 1 low-x 2012 CyprusSoft Processes at LHC in PYTHIA8 K. Goulianos1 * with: Robert Ciesielski

2. CONTENTS low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 2

3. 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!

4. STUDIES OF DIFFRACTION IN QCD Diffractive  Colorless vacuum exchange  large-gap signature Non-diffractive  color-exchange  gaps exponentially suppressed POMERONPOMERON Goal : probe the QCD nature of the diffractive exchange rapidity gap Incident hadrons acquire color and break upart CONFINEMENT Incident hadrons retain their quantum numbers remaining colorless p ppp p low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 4

5. DEFINITIONS MXMX dN/d  ,t,t p’ Rap-gap  =-ln  0 ln s ln Mx 2 ln s since no radiation  no price paid for increasing diffractive gap size low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos pp p MXMX p p’ SINGLE DIFFRACTION 5

6. DIFFRACTION AT CDF Single Diffraction or Single Dissociation Double Diffraction or Double Dissociation Double Pom. Exchange or Central Dissociation Single + Double Diffraction (SDD) SD DD DPE /CD SDD Elastic scatteringTotal cross section  T =Im f el (t=0) OPTICAL THEOREM   gap   low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos JJ, b, J/   W p p JJ …ee…  exclusive 6

7. 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,t p p p’ √s=22 GeV RENORMALIZATION Regge FACTORIZATION BREAKING IN SOFT DIFFRACTION CDFCDF  Question: does factorization breaking affect t-distributions? low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 7

8. EDS-2011 Vietnam CDF Diffraction and Exclusive Production 8 DD at CDF renormalized gap probabilityx-section

9. EDS-2011 Vietnam CDF Diffraction and Exclusive Production 9 SDD at CDF  Excellent agreement between data and MBR (MinBiasRockefeller) MC

10. 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

11. 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 DD CD

12. Total, elastic, and inelastic x-sections low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 12 GeV 2

13. Total, elastic, and inelastic x-sections versus √s low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 13

14. Difractive x-sections low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 14  1 =0.9,  2 =0.1, b 1 =4.6 GeV -2, b 2 =0.6 GeV -2, s′=s e -  y,  =0.17,  2 (0)=  0, s 0 =1 GeV 2,  0 =2.82 mb or 7.25 GeV -2

15. 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  y S =2 for SD and DD, and  y=  y 1 +  y 2 =2 for CD (DPE).

16. 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).

17. 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

18. low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos Thank you for your attention 18

19. References in arXiv:1205.1446v1 [hep-ph] low-x 2012 Cyprus Soft Processes at LHC in PYTHIA8 K. Goulianos 19 multiplicities