The Monash 2013 Tune of PYTHIA 8

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1 he Monash 3 une of PYHIA Peter Skands (CERN) Current Default = C (from ) LEP tuning undocumented (from 9) LHC tuning only used very early data + S. Rojo & S. Carrazza recently added a new PDF set: NNPDF.3 LO (αs(mz)=.3) Aims for the Monash 3 une Revise (and document) constraints from e + e - measurements In articular in light of ossible interlays with LHC measurements! est drive the new NNPDF LO PDF set for / bar Udate min-bias and UE tuning + energy scaling 3 Follow Perugia tunes for PYHIA : use same αs for ISR and FSR Use the PDF value of αs for both hard rocesses and MPI In Pythia.5 +writeu available soon Worksho on Forward Physics and Diffraction CERN, February

2 LEP : Nch & x = /MZ Slightly lower large-nch tail Slightly softer ultra-hard tail ) Probability(n ch heory/data Charged Multilicity (udsc) Data from Phys.Ret. 399 () 7 Pythia.3 L3.5 ±..7 ±.. ±. n ch V I N C I A R O O /<n ch > dn ch /dx - Changes only to highly suressed tails. - Exect minimal imact on overall modelling heory/data.. Charged Momentum Fraction Data from Barate et al., Phys. Re. 9 (99) Pythia.3 ALEPH ±.. ±. ±... x V I N C I A R O O Note: these fragmentation arameters go directly into the modelling of diffraction

3 Strangeness % More Strangeness ch > <n <n> Meson Fractions LEP + SLD ±.. ±.. ±. ch > <n <n> - Baryon Fractions LEP. ±.. ±.. ±. - - % More - Data from PDG/HEPDAA Pythia.3 V I N C I A R O O Data from PDG/HEPDAA Pythia.3 V I N C I A R O O heory/data.. π ± π ± K ' ρ ± (less vector mesons) ρ *± K ω φ K*/K- R R φ/ π- R φ /K- R φ /K* heory/data.. Λ R /K R Λ Λ/ Σ ± Σ ++ * Σ ± Ξ * Ξ Ω Consistency: Rates of Ds and Bs also imrove. Kaon fraction at LHC also imroves 3

4 Strangeness: scaling <n K > +/- Average K HEPDAA Multilicity vs ECM ±.. ±.. ±. <n Λ >.5 Average Λ HEPDAA Multilicity vs ECM.5 ±.. ±.. ±..5 heory/data.. Short Strings Data from HEPDAA Pythia.3 Long Strings k 3.k E cm (not to scale) V I N C I A R O O heory/data.. Short Strings Data from HEPDAA Pythia.3 Long Strings k 3.k E cm (not to scale) V I N C I A R O O Consistency: imrovements reeated across all ee energies

5 OEM AL PYHIA PYHIA ALICE ALICE AUGER AUGER PP: the otal Cross Section Pileu rate tot(s) = el (s)+ inel (s) / s. or ln (s)? PP CROSS SECIONS OEM, PRL (3), Donnachie-Landshoff (.9?) Froissart-Martin Bound tot(3 ev) ± mb PYHIA: mb OEM OEM inel(3 ev) ± 3.5 mb PYHIA: 7 mb 3 ev (.9%) tot( ev) = ±.9 mb PYHIA: 93 mb total inelastic 7 ev ev (.3%) inel( ev) = 7.7 ±.7 mb PYHIA: 73 mb elastic PYHIA elastic is too low (5.%) el( ev) = 7. ±. mb PYHIA: mb (PYHIA versions:.. &..) 5

6 ) Prob(n Ch heory/data Charged-Particle Multilicities GeV Soft Chg. Mult. (n Charged Particle: ND/SD/DD Shown with/without diffractive tag in. Martin s talk yesterday he enhancement of double dissociation in AFP tagged events with PYHIA is nicely contained at low overall charged article multilicity ( <.5). Charged Particle: PY/H++/EPOS Good Also seen degree in AFLA, of model but searation to a lesser observed extent as when more comaring single di raction the generators. is accessable. dn Ev /d d /d Ev - Ch Data from New J.Phys. 3 () 5333 Pythia. ALAS PY (Monash 3) PY (C) PY (C) > MeV. ±. 5.3 ±.. ±. 5 5 of n Ch V I N C I A R O O dn Ev /d d /d Ev /d> ch <dn NSD /n heory/data GeV Like - with the energy flow, EPOS shows- no sign of any asymmetry in flow., >., <.5) s = ev <dn Ev of [AFP] PYHIA A [AFP] HERWIG++ UE-EE [AFP] EPOS LHC PYHIA A HERWIG++ UE-EE EPOS LHC s = ev [AFP] PYHIA A: ND > MeV [AFP] PYHIA A: SD [AFP] PYHIA A: DD PYHIA A ND PYHIA A SD PYHIA A DD Ev s = chev > MeV [ALFA] PYHIA A [ALFA] HERWIG++ UE-EE [ALFA] EPOS LHC PYHIA A HERWIG++ UE-EE EPOS LHC s = ev [ALFA] PYHIA A: ND > MeV[ALFA] PYHIA A: SD [ALFA] PYHIA A: DD PYHIA A ND PYHIA A SD PYHIA A DD /d> (NSD) PY (Monash 3) PY (C) PY (C) Project out tagged comonents Searation Data from Phys.Rev.Lett. 5 () Pythia. - - (Note: here standard ones, without fwd tag). ±.. ±..9 ±. V I N C I A R O O

7 /d> Ch <dn otem /n heory/data Going Forward Shown with/without diffractive tag in. Martin s talk yesterday Forward tag greatly enhances sread of model redictions. 7 GeV <dn /d> (n, >., 5.3< <.5) Ch ch of Pythia. OEM PY (Monash 3) PY (C) PY (C) Data from Eurohys.Lett. 9 () 3. ±.. ±.. ± V I N C I A R O O <de/d> s = ev, Ch(Neutral) 7 GeV MB Fwd E Flow (n in both 3.3< <.5) ch PY (Monash 3) PY (C) PY (C) > 5() MeV [ALFA] PYHIA A [ALFA] HERWIG++ UE-EE [ALFA] EPOS LHC PYHIA A HERWIG++ UE-EE EPOS LHC Data from JHEP () Pythia.. ±.. ±.. ± Increased <Nch> in OEM accetance. Slightly steeer FWD E flow. heory/data.. V I N C I A R O O 7

8 Summary Aologies: did not do dedicated study of diffraction E.g., ga-size distributions not included, though interesting Revised ee fragmentation arameters and tune using new NNPDF.3 LO PDF set Increased strangeness and more forward activity Low-multilicity region and strangeness sectra still challenging! Pythia.5 Monash 3 une:ee=7; une: = ; Work underway: Imroved colour-reconnection model (PS + J.R. Christiansen) Inclusion of diffractive Z (. Sjostrand + C. Rasmussen)

9 distributions and Fragmentation dn K /d /n K - 7 GeV KS ( y <., NSD) PY (Monash 3) PY (C) PY (C) 7. ±. 3.3 ±.. ±. dn φ /d /n φ 7 GeV φ (INEL, y <.5, >.) ALICE PY (Monash 3) PY (C) PY (C). ±.. ±. 3. ±. dn Λ /d /n Λ - 7 GeV Λ ( y <., NSD) PY (Monash 3) PY (C) PY (C) 5. ±..7 ±.3.3 ± heory/data KS hi Lambda Data from JHEP 5 () Pythia. [GeV] V I N C I A R O O heory/data.. Data from Eur.Phys.J. C7 () 3 Pythia. [GeV] V I N C I A R O O heory/data -5.. Data from JHEP 5 () Pythia. [GeV] V I N C I A R O O 9