Soft QCD Results from ATLAS and CMS

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1 Soft QCD Results from ALAS and Moriond, March

2 oics Proerties of minimum bias events - transverse momentum, seudoraidity and event-by-event multilicity distributions of charged articles Underlying event characteristics - from charged article tracks (ALAS, ) - from calorimeter information (recent ALAS analysis, not art of talk) Studied observables (non-exhaustive): charged article multilicity density charged article scalar density charged article mean angular distributions Strangeness roduction Particle correlations - Bose-Einstein correlations - short-range and long-range angular correlations in and Pb-Pb events C.-E. Wulz Moriond, March

Minimum Bias, Underlying Event Ideally Minimum Bias events are those recorded with a totally inclusive

$Usually Minimum Bias only refers to non-single diffractive (NSD) events.$ It has comonents from multile semi-hard arton scattering rocesses and soft comonents from beam-beam

It has comonents from multile semi-hard arton scattering rocesses and soft comonents from beam-beam

Leading track or (track) jet direction Δφ < 6 Δφ > Beam Picku iming for exeriments (BPX) z = ±75 m,

3 Minimum Bias, Underlying Event Ideally Minimum Bias events are those recorded with a totally inclusive trigger. he exact definition deends on the exeriment, in articular the trigger. Usually Minimum Bias only refers to non-single diffractive (NSD) events. Underlying event comrises all articles excet the (hard) rocess of interest. It has comonents from multile semi-hard arton scattering rocesses and soft comonents from beam-beam remnants. he region transverse to the dominant momentum flow is most sensitive to the underlying event. Leading track or (track) jet direction Δφ < 6 Δφ > Beam Picku iming for exeriments (BPX) z = ±75 m, time resolution. ns ALAS Min. Bias rigger Scintillators (MBS) stations at z = ±.56 m,.9 < η <.8,.8 < η <.84 C.-E. Wulz Beam Scintillator Counters (BSC) z = ±.86 m,. < η < 4.65 Moriond, March

4 ransverse momentum sectra Inclusive invariant cross-section x scaling curve c ] - [GeV N/d DAA / MC Ed (b) s = 7 ev,! <.4 " Ldt =.96 b PYHIA D6 PYHIA Perugia PYHIA ProQ PYHIA 8 Preliminary - c ] - [mb GeV!/d Ed 4.9 s/gev) ( (a) + - () #.5(h +h ) + X ( " <.) - 7 ev (.96 b ).9 ev ( CDF.96 ev CDF.8 ev CDF ev - µb ) UA.9 ev ( " <.5) UA.5 ev ( " <.5) UA. ev ( " <.5) Preliminary x = / s [GeV/c] -4 - x - - PAS QCD--8 = F (x d )/ n(x, s) = F (x )/ s n(x, s) E d σ C.-E. Wulz 4 Moriond, March

5 / d! d /N ev " Minimum Bias seudoraidity distributions Charged article multilicities versus seudoraidity at 9 GeV and 7 ev n ch #, > 5 MeV,! <.5 ALAS s =.9 ev / d! d /N ev " n ch #, > 5 MeV,! <.5 ALAS s = 7 ev Ratio Data 9 PYHIA ALAS AMB PYHIA ALAS MC9 PYHIA DW PYHIA 8 PHOJE. Data Uncertainties MC / Data Ratio Data PYHIA ALAS AMB PYHIA ALAS MC9 PYHIA DW PYHIA 8 PHOJE. Data Uncertainties MC / Data ! he-ex.54v, acceted by New J. Physics ! C.-E. Wulz 5 Moriond, March

6 Minimum Bias multilicity distributions n ch, > MeV, η.5 9 GeV 7 ev! dn ev /dn ch - n ch #, > MeV, " <.5 ALAS s =.9 ev! dn ev /dn ch - n ch #, > MeV, " <.5 ALAS s = 7 ev /N ev - /N ev Ratio Data 9 PYHIA ALAS AMB PYHIA ALAS MC9 PYHIA DW PYHIA 8 PHOJE Data Uncertainties MC / Data Ratio Data PYHIA ALAS AMB PYHIA ALAS MC9 PYHIA DW PYHIA 8 PHOJE Data Uncertainties MC / Data n ch he-ex.54v, acceted by New J. Physics n ch C.-E. Wulz 6 Moriond, March

7 / d ev ) dn ev (/N / "# "("!) " 7/.9 ev / N ev Data 7 ev Data.9 ev PYHIA-6 Z, 7 ev PYHIA-6 Z,.9 ev Data PYHIA-6 D6 PYHIA-6 Z PYHIA-8 4C Preliminary charged articles ( >.5 GeV/c, # <, 6 < "! < ) ing track-jet > GeV/c Preliminary Multilicity density ratio 7 ev/.9 ev charged articles ( >.5 GeV/c, # <, 6 < "! < ) Leading track-jet [GeV/c] Charged article distributions ] - [(GeV/c) / d d / "# "("!) [GeV/c] $ " 7/.9 ev /N ev Data 7 ev Data.9 ev PYHIA-6 Z, 7 ev Data PYHIA-6 D6 PYHIA-6 Z PYHIA-8 4C Preliminary PYHIA-6 Z,.9 ev charged articles < "! < ) ( >.5 GeV/c, # <, 6 ing track-jet > GeV/c [GeV/c] Preliminary Sum density ratio 7 ev/.9 ev charged articles ( >.5 GeV/c, # <, 6 < "! < ) Leading track-jet [GeV/c] / "# "("!) [GeV/c] $ " / N ev Data 7 ev PYHIA-6 D6 PYHIA-6 Z PYHIA-8 4C charged articles ( >.5 GeV/c, # <, 6 < "! < ) Leading track-jet [GeV/c] ransverse regions Strong growth of underlying event activity with s. PYHIA Z describes the distributions and the s deendence well. PAS QCD-- Preliminary C.-E. Wulz 7 Moriond, March

8 Charged article multilicity density ransverse region /d"d!> <d.6.4. ransverse Region >.5 GeV and " <.5 ALAS s = 7 ev /d"d!> <d.5 ransverse Region >. GeV and " <.5 ALAS s = 7 ev.5.4. Data PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 PYHIA DW PYHIA Perugia PHOJE.5 Data PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 PYHIA DW PYHIA Perugia PHOJE wo-fold increase in multilicity for >. GeV comared to >.5 GeV All models underestimate the multilicity by at least -5%, but PYHIA DW comes closest for >.5 GeV. HERWIG/JIMMY roduce more articles between MeV and 5 MeV than other models..4. he-ex.79v, submitted to Phys. Rev. D C.-E. Wulz 8 Moriond, March

9 Charged article scalar sum density oward region ransverse region /d"d!> # <d oward Region >.5 GeV and " <.5 Data PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 ALAS s = 7 ev PYHIA DW PYHIA Perugia PHOJE /d"d!> # <d ransverse Region >.5 GeV and " <.5 Data PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 ALAS s = 7 ev PYHIA DW PYHIA Perugia PHOJE he transverse region lateau characterizes the mean contribution of the underlying event to jet energies, whereas in the toward and away regions jetlike rofiles are resent. PYHIA DW describes both regions best. Other Monte Carlo rograms describe the transverse region in articular quite oorly..4. he-ex.79v, submitted to Phys. Rev. D C.-E. Wulz 9 Moriond, March

10 > < > < Charged article mean at 9 GeV and 7 ev ransverse Region >.5 GeV and! <.5 Data 9 PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 ALAS s = 9 GeV PYHIA DW PYHIA Perugia PHOJE Increase of underlying event < > by about % from s = 9 GeV to s = 7 ev. ransverse Region >.5 GeV and! <.5 Data PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 ALAS s = 7 ev PYHIA DW PYHIA Perugia PHOJE he-ex.79v, submitted to Phys. Rev. D C.-E. Wulz > < > < oward Region oward Region >.5 GeV and! <.5 Data 9 PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 >.5 GeV and! <.5 Data PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 ALAS s = 9 GeV PYHIA DW PYHIA Perugia PHOJE ALAS s = 7 ev PYHIA DW PYHIA Perugia PHOJE > < > < Away Region >.5 GeV and! <.5 Away Region Data 9 PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 >.5 GeV and! <.5 Data PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 ALAS s = 9 GeV ALAS s = 7 ev PYHIA DW PYHIA Perugia PHOJE PYHIA DW PYHIA Perugia PHOJE Moriond, March

11 Angular distributions /d# d"! /d# d"! d d >.5 GeV, ing article excluded s = 7 ev Data PYHIA ALAS MC9 PYHIA DW PYHIA Perugia PHOJE HERWIG+JIMMY ALAS MC9 >. GeV Away ransverse oward ransverse Away >. GeV Away ransverse oward ransverse Away >.5 GeV and # <.5 >. GeV ALAS Away ransverse oward ransverse Away > 5. GeV "! [rad] "! [rad] wrt wrt Away ransverse oward ransverse Away /d# d"! $ d /d# d"! $ d Significant shae difference between data and MC. With increasing jet-like structure develos. PYHIA tunes redict stronger correlation in toward region. s = 7 ev Data PYHIA ALAS MC9 PYHIA DW PYHIA Perugia PHOJE HERWIG+JIMMY ALAS MC9 >. GeV Away ransverse oward ransverse Away >. GeV >.5 GeV and # <.5 >. GeV ALAS Away ransverse oward ransverse Away > 5. GeV φ distribution (Δφ wrt to the ing article) of charged article multilicity densities he-ex.79v, submitted to Phys. Rev. D.5 Away ransverse oward ransverse Away Away ransverse oward ransverse Away "! [rad] "! [rad] wrt wrt φ distribution (Δφ wrt to the ing article) of sum densities C.-E. Wulz Moriond, March

Correlations Charged article mean versus multilicity > <.5.4... ransverse Region >.5 GeV and! <.5 ALAS s = 7 ev > <..8.6.4 oward Region >.5 GeV and! <.5 ALAS s = 7 ev.9.

12 Correlations Charged article mean versus multilicity > < ransverse Region >.5 GeV and! <.5 ALAS s = 7 ev > < oward Region >.5 GeV and! <.5 ALAS s = 7 ev.9..7 Data PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 PYHIA DW PYHIA Perugia PHOJE Data PYHIA ALAS MC9 HERWIG+JIMMY ALAS MC9 PYHIA DW PYHIA Perugia PHOJE Monotonic increase of < > with in transverse and away regions. In the toward region, for > 5 a jet-like structure forms and < > rises weakly. PHOJE gives best descrition at 7 ev. he-ex.79v, submitted to Phys. Rev. D C.-E. Wulz Moriond, March

13 Candidates / MeV/c Candidates / MeV/c # $ s = 7 ev 48 µb - s = 7 ev Strangeness roduction (K S, Λ, Ξ) " + "! invariant mass [MeV/c ] 48 µb - Yield: 654 # Mean: MeV/c Avg $: 8. MeV/c K S Yield: 4.4 $ Mean:. MeV/c Avg %: 4. MeV/c 5 4 #"! invariant mass [MeV/c ] he-ex.48v, submitted to JHEP C.-E. Wulz Ξ - (GeV/c) ) dn / d NSD (/N - (GeV/c) ) dn / d NSD (/N [GeV/c] K S s = 7 ev s =.9 ev "! [GeV/c] s = 7 ev s =.9 ev ) dn / dy (/N NSD ) dn / dy (/N NSD s = 7 ev PYHIA6 D6 PYHIA6 P PYHIA8.5.5 K y s = 7 ev PYHIA6 D6 PYHIA6 P PYHIA8 s =.9 ev PYHIA6 D6 PYHIA6 P PYHIA8 s =.9 ev PYHIA6 D6 PYHIA6 P PYHIA8.5.5 "! y Moriond, March S

14 Strangeness roduction (K S, Λ, Ξ) MC / Data K S MC / Data # MC / Data "! ev PYHIA6 D6 7 ev PYHIA6 P 7 ev PYHIA ev PYHIA6 D6.9 ev PYHIA6 P.9 ev PYHIA [GeV/c] ) N(!) / N(K N(# " ) / N(!) S ev ev ev ev ev 7 ev ev [GeV/c] N stays aroximately constant for both centre-of-mass energies. he-ex.48v, submitted to JHEP C.-E. Wulz 4 Moriond, March

15 dn/dq =( )/( dnref /dq Double ratio /. GeV Bose-Einstein correlations Pairs of same-sign charged articles with. GeV < Q < GeV are studied. RMC R(Q) R(Q) = R R(Q) = - s = 7 ev MC: PYHIA 6.4 tune Z R(Q) =(dn/dq)/(dn ref /dq) R(Q) =C[ + λω(qr)]( + δq) R R MC Q (GeV) =( dn/dq dn ref /dq )/( dn MC/dQ dn MC,ref /dq ) Reference samle: oosite-sign airs, mixed events etc. λ correlation strength r. radius of effective sace-time region emitting bosons with overlaing wave functions Ω Fourier transform of the region defined by r he-ex.58v, submitted to JHEP C.-E. Wulz 5 r (fm)!.5 - s = 7 ev s = 7 ev r =.89 ±. (stat.) ±.9 (syst.) fm k (GeV) λ = 8 ±.9 (stat.) ±.9 (syst.) range: ( - 9) range: ( - 4) range: (5-8) k (GeV) k = + / Q = ( ) Moriond, March

16 Anticorrelations R(Q) =C[ + λ(cos[(r Q) + tan(απ/4)(qr) α ]e (Qr)α )]( + δq) PLB 66 (84) Double ratio /. GeV s = 7 ev exonential Eq. (4) Q (GeV) Anticorrelations between same-sign charged articles are observed for Q values above the signal region.! Double ratio /. GeV s =.9 ev exonential Eq. (4) Q (GeV) s =.9 ev s = 7 ev he-ex.58v, submitted to JHEP Δ deth of the di in the anticorrelation region C.-E. Wulz 6 Moriond, March.5

17 Near-side long-range correlations in data JHEP 9 () 9 First surrise in LHC data! 7 ev AA * Ridge does not come from short range correlations such as resonances, near-side jet eaks, away side correlations of articles between back-toback jets or Bose-Einstein correlations. Pronounced structure (ridge) in high-multilicity events for. < Δη < 4.8 and Δφ C.-E. Wulz 7 Moriond, March

18 Long- and short-range correlations in ion data Short-range (< Δη <): Jet + Ridge AA * Long-range (< Δη <4): Ridge PbPb.76 ev/nucleon Ridge most evident for GeV < trig < 6 GeV, but disaears at high C.-E. Wulz 8 Moriond, March

Conclusions Understanding of soft QCD contributions is crucial for new hysics searches and recision measurements of Standard Model rocesses.

19 Conclusions Understanding of soft QCD contributions is crucial for new hysics searches and recision measurements of Standard Model rocesses. Pre-LHC Monte Carlo tunes do not describe the data well in all asects. Much more tuning is needed. Strangeness roduction has been investigated and Bose-Einstein correlations have been studied in detail. Interesting long-range correlations have been observed, both in roton and heavy ion data. C.-E. Wulz 9 Moriond, March

Other ATLAS Jet Measurements

Other ATLAS Jet Measurements Other ALAS Jet Measurements Michael Begel Aril, Jets as Hard Probes Michael Begel Standard Model @ LHC ALAS Jet Measurements Aril, High dijet roduction rovides a owerful robe of the hard scatter recision