Mul1plicity dependence of strange and mul1- strange hadron produc1on in pp collisions at s=7 TeV measured with the ALICE experiment

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1 XLV Internaonal ymosium on Mularcle Dynamics Wildbad Kreuth, 4 9 Oct 5 Mullicity deendence of strange and mul strange hadron roducon in collisions at s=7 ev measured with the ALICE exeriment Rafael Derradi de ouza For the ALICE Collaboraon UNICAMP Brazil (suorted by FAPEP Grant 4/967 8)

2 Outline Introducon A A, A and systems he ALICE Exeriment Mullicity elecon Forward raidity esmator trange Hadron Measurements K, Λ, Ξ and Ω Results ummary R.D. de ouza IMD 5 7 October 5

3 Introducon: A A, A and A A: Large system: deconfinement/ PRL (). =. ev QGP scenario trangeness enhancement Λ/K enhancement at intermediate, Λ/K Λ/K y <.5 AR: AuAu at snn /K 5% Λ/K /K 68% Λ/K Λ 5% Λ 68% ALICE: PbPb at Λ/K Λ/K 5% s NN =.76 ev 68% systematic uncertainty heory 5% Hydro VIH+ Recombination EPO ffiffiffiffiffiffiffiffi R.D. de ouza IMD 5 7 October 5

4 Introducon: A A, A and A A: A: Large system: deconfinement/ QGP scenario trangeness enhancement Λ/K enhancement at intermediate Intermediate system: suited to exlore the transion between A A and Progressive release of canonical suression Λ/K qualitavely similar to A A, Λ/K Λ/K PRL () y <.5 AR: AuAu at snn /K 5% Λ/K /K 68% Λ/K ALICE: PbPb at Λ/K Λ/K 5% =. ev Λ 5% Λ 68% s NN =.76 ev 68% systematic uncertainty heory 5% Hydro VIH+ Recombination EPO Phys. Lee. B 78 (4) 5 8 ffiffiffiffiffiffiffiffi R.D. de ouza IMD 5 7 October 5 Fig.. (Color online.) Ratios K/π = (K + +K )/(π + +π ),/π = (+ )/(π +

5 Introducon: A A, A and A A: A: : Large system: deconfinement/ QGP scenario trangeness enhancement Λ/K enhancement at intermediate Intermediate system: suited to exlore the transion between A A and Progressive release of canonical suression Λ/K qualitavely similar to A A mall system: no collecvity or deconfinement exected Reference for A A (hadron gas), Λ/K Λ/K PRL () y <.5 AR: AuAu at snn /K 5% Λ/K /K 68% Λ/K ALICE: PbPb at Λ/K Λ/K 5% =. ev Λ 5% Λ 68% s NN =.76 ev 68% systematic uncertainty heory 5% Hydro VIH+ Recombination EPO Phys. Lee. B 78 (4) 5 8 ffiffiffiffiffiffiffiffi R.D. de ouza IMD 5 7 October 5 Fig.. (Color online.) Ratios K/π = (K + +K )/(π + +π ),/π = (+ )/(π +

6 Introducon: A A, A and A A: A: : Large system: deconfinement/ QGP scenario trangeness enhancement Λ/K enhancement at intermediate Intermediate system: suited to exlore the transion between A A and Progressive release of canonical suression Λ/K qualitavely similar to A A mall system: no collecvity or deconfinement exected Reference for A A (hadron gas), Λ/K Λ/K PRL () y <.5 AR: AuAu at snn /K 5% Λ/K /K 68% Λ/K ALICE: PbPb at Λ/K Λ/K 5% =. ev Λ 5% Λ 68% s NN =.76 ev 68% systematic uncertainty heory 5% Hydro VIH+ Recombination EPO Phys. Lee. B 78 (4) 5 8? ffiffiffiffiffiffiffiffi What about mul+licity deendence in? R.D. de ouza IMD 5 7 October 5 Fig.. (Color online.) Ratios K/π = (K + +K )/(π + +π ),/π = (+ )/(π +

7 he ALICE Exeriment R.D. de ouza IMD 5 7 October 5 4

8 he ALICE Exeriment Detectors used in this analysis: PC ( η <.9) Gas filled ionizaon detecon volume racking, vertex, PID (de/dx) R.D. de ouza IMD 5 7 October 5 4

9 he ALICE Exeriment Detectors used in this analysis: PC ( η <.9) Gas filled ionizaon detecon volume racking, vertex, PID (de/dx) I ( η <.9) 6 Layers of silicon detectors rigger, tracking, vertex, PID (de/dx) R.D. de ouza IMD 5 7 October 5 4

10 he ALICE Exeriment Detectors used in this analysis: PC ( η <.9) Gas filled ionizaon detecon volume racking, vertex, PID (de/dx) I ( η <.9) 6 Layers of silicon detectors rigger, tracking, vertex, PID (de/dx) V [VA (.8<η<5.) & VC (.7<η<.7)] Forward arrays of scinllators rigger, beam gas rejecon Mullicity esmaon VA VC R.D. de ouza IMD 5 7 October 5 4

11 he ALICE Exeriment VA R.D. de ouza IMD 5 7 October 5 VC Detectors used in this analysis: PC ( η <.9) Gas filled ionizaon detecon volume racking, vertex, PID (de/dx) I ( η <.9) 6 Layers of silicon detectors rigger, tracking, vertex, PID (de/dx) V [VA (.8<η<5.) & VC (.7<η<.7)] Forward arrays of scinllators rigger, beam gas rejecon Mullicity esmaon Mul@licity elec@on Event selecon erformed via ercenles of the VM amlitude distribuon (VA + VC) <dn /dη> esmated as the average number of rimary arged tracks in η <.5 4

12 trange Hadron Measurements V s (single strange hadrons) Cascades (mul@ strange hadrons) K! + +! +! + + B.R.: 6.9% cτ: 7.89 cm mass: 5.68 MeV/c d s! + +! + + B.R.: 69.% cτ:.68 cm B.R.: 99.9% mass: MeV/c cτ: 4.9 cm uds ū d s s d mass:.7 MeV/c! + K +! + K + B.R.: 67.8% cτ:.46 cm mass: MeV/c dss d s s sss s s s R.D. de ouza IMD 5 7 October 5 6

13 trange Hadron Measurements V Decay oology elecon Variables: 5 Counts / (MeV/c ) % VM Mult.Class ALICE Performance < s=7ev η <.5 <. GeV/c K Counts / (MeV/c ) 5 % VM Mult.Class ALICE Performance < s=7ev η <.5 <. GeV/c Λ ALI PERF 7 R.D. de ouza IMD 5 7 October M π + π (GeV/c ) ALI PERF M π (GeV/c ) 7

14 trange Hadron Measurements Cascade Decay oology elecon Variables: Counts / (MeV/c ) % VM Mult.Class ALICE Performance < s=7ev η <.5 <. GeV/c Ξ M (GeV/c Λπ ) ALI PERF 74 Counts / (MeV/c ) % VM Mult.Class ALICE Performance.6 < s=7ev η <.5 <. GeV/c Ω 5 4 R.D. de ouza IMD 5 7 October 5 ALI PERF M (GeV/c ΛK ) 8

15 Results: ectra (I) dy ) N/(d d ALICE Preliminary s = 7 ev K y <.5 dy ) N/(d d ALICE Preliminary s = 7 ev Λ+Λ y <.5 /N ev /N ev Levysallis fit VM multilicity event classes 9 % (x ) 8 5% (x ) 7 5% (x ) 6 5% (x ) 5 5% (x ) 4 % (x ) 4% (x ) 45% (x ) 57% (x) 7% Levysallis fit VM multilicity event classes 9 % (x ) 8 5% (x ) 7 5% (x ) 6 5% (x ) 5 5% (x ) 4 % (x ) 4% (x ) 45% (x ) 57% (x) 7% Ratio to [%] Ratio to [%] ALI PREL ot. yst uncertainty on ratio R.D. de ouza IMD 5 7 October 5 ALI PREL ot. yst uncertainty on ratio

16 Results: ectra (I) dy ) N/(d d ALICE Preliminary s = 7 ev K y <.5 dy ) N/(d d ALICE Preliminary s = 7 ev Λ+Λ y <.5 /N ev /N ev 4 4 Ratio to [%] Levysallis fit VM multilicity event classes 9 % (x ) 8 5% (x ) 5% (x 7 ) 5% (x 6 ) 5 5% (x ) 4 % (x ) 4% (x ) 45% (x ) 57% (x) 7% % (x ) % (x ) 4% (x ) ) Raos seem to saturate for 45% (x above 8 aroximately 57% (x) 7% GeV/c 5 6 Levysallis fit VM multilicity event classes 9 % (x ) 8 5% (x ) 5% (x 7 ) 6 5% (x ) ectra become harder for higher mullicies Ratio to [%] ALI PREL ot. yst uncertainty on ratio R.D. de ouza IMD 5 7 October 5 ALI PREL ot. yst uncertainty on ratio

17 Results: ectra (II) dy) N /(d d ALICE Preliminary s=7ev + Ξ +Ξ y <.5 dy) N /(d d ALICE Preliminary s=7ev + Ω +Ω y <.5 /N ev 4 /N ev 4 5 Levysallis fit 5 Levysallis fit 6 7 VM multilicity event classes 7 % ( ) 6 5% ( ) 5 5% ( ) 4 5% ( ) 5% ( ) 5% ( ) 57% ( ) 7% 6 VM multilicity event classes 4 5% ( ) 55% ( ) 5% ( ) 5% ( ) 5% Ratio to [%] Ratio to [%] ALI PREL ot. yst uncertainty on ratio R.D. de ouza IMD 5 7 October 5 ALI PREL 9896 ot. yst uncertainty on ratio 4 5 6

18 Results: ectra (II) dy) N /(d d ALICE Preliminary s=7ev + Ξ +Ξ y <.5 dy) N /(d d ALICE Preliminary s=7ev + Ω +Ω y <.5 /N ev 4 /N ev 4 5 Levysallis fit 5 Levysallis fit 6 7 VM multilicity event classes 7 % ( ) 6 5% ( ) 5 5% ( ) 4 5% ( ) 5% ( ) 5% ( ) 57% ( ) 7% 6 imilarly as for K and Λ VM multilicity event classes 4 5% ( ) 55% ( ) 5% ( ) 5% ( ) 5% Ratio to [%] Ratio to [%] ALI PREL ot. yst uncertainty on ratio R.D. de ouza IMD 5 7 October 5 ALI PREL 9896 ot. yst uncertainty on ratio 4 5 6

19 Results: < >.8.6 ALICE Preliminary y <.5 s=7 ev.4. Rising trend of < > as a funcon of mullicity for all idenfied arcles (dashed lines are logarithmic fits to guide the eye) ALI PREL 9975 π + +π φ + K +K Λ+ Λ + K + Ξ +Ξ Logarithmic fit Ω +Ω + dn /dη η <.5 he deendence of the < > with mullicity shows the hardening of the sectra clearly R.D. de ouza IMD 5 7 October 5

20 Results: Λ/K vs in Λ/K.8 ALICE Preliminary s = 7 ev VM Multilicity Classes: %, dn /dη =. 7%, dn /dη =. %, dn /dη = 6. Λ/K as a funcon of for highest ( %) and lowest (7 %) mullicity selecons comared to the mullicity integrated ( %) selecon.6.4. è è è Clear searaon between highest and lowest mullicity selecons he osion of the maximum is shited he trend observed for the mullicity integrated case seems closer to the one observed for the highest mullicity selecon ALI PREL R.D. de ouza IMD 5 7 October 5

21 Results: Λ/K vs in, Pb, Pb Pb Pb, Pb Pb: ALICE, PLB 78 (4) 5 8 Λ/K.8.6 ALICE Preliminary s = 7 ev %, dn /dη =. 7%, dn /dη =. (VM Multilicity Classes) ALICE Pb s NN = 5. ev 5%, dn /dη = %, dn /dη = 9.8 (VA Mult. Classes Pb side) ALICE PbPb s NN =.76 ev 5%, dn /dη = 6. 89%, dn /dη = ALI PREL he deendence of the rao with the event mullicity in seems qualitavely similar to what is observed for Pb and Pb Pb R.D. de ouza IMD 5 7 October 5

22 Results: Λ/π vs mullicity in +π + ) Λ / (π 5 4 GIHeidelberg model PbPb =56 MeV HERMU V. model =56 MeV PbPb Consistent behavior observed between the results from and Pb Good agreement with INEL at low mullicies ALICE Preliminary Pb s NN =5. ev GC saturaon value reaed in the higher mullicies VA Mult. Evt. Classes (Pbside) (INEL) PbPb s=7 ev s NN =.76 ev Preliminary s=7 ev ALI PREL VM Mult. Evt. Classes dn /dη η <.5 R.D. de ouza IMD 5 7 October 5 4

23 Results: Λ/π vs mullicity in +π + ) Λ / (π 5 4 GIHeidelberg model PbPb =56 MeV HERMU V. model =56 MeV PbPb Consistent behavior observed between the results from and Pb Good agreement with INEL at low mullicies ALICE Preliminary Pb s NN =5. ev GC saturaon value reaed in the higher mullicies VA Mult. Evt. Classes (Pbside) ALI PREL 9895 MC roductions s=7ev Pythia6PerugiaNoCR Pythia6PerugiaWithCR Pythia8MonashWithCR (INEL) PbPb Preliminary dn s=7 ev s NN =.76 ev s=7 ev VM Mult. Evt. Classes /dη η <.5 Pythia 6 and 8 redicons using several tunes show strong disagreement with the observed trend in collisions Effects of color reconnecon (CR) in the simulaon does not roduce significant anges R.D. de ouza IMD 5 7 October 5 4

24 Results: Ξ/π and Ω/π vs mult. in +π + ) ) / (π + +Ξ (Ξ GIHeidelberg model PbPb =56 MeV HERMU V. model PbPb =55 MeV + π + ) ) / (π + + Ω.8 GIHeidelberg model PbPb =56 MeV MC roductions s=7ev Pythia6PerugiaNoCR Pythia6PerugiaWithCR Pythia8MonashWithCR HERMU V. model PbPb =55 MeV 4 (Ω.6 ALI PREL 9875 MC roductions s=7ev Pythia6PerugiaNoCR Pythia6PerugiaWithCR Pythia8MonashWithCR R.D. de ouza IMD 5 7 October 5 ALICE Preliminary Pb s NN = 5. ev VA Mult. Evt. Classes (Pbside) (INEL) s = 9 GeV (INEL) s = 7 ev PbPb s NN =.76 ev Preliminary s = 7 ev VM Mult. Evt. Classes dn /dη η <.5.4. ALI PREL ALICE Preliminary Pb s NN = 5. ev VA Mult. Evt. Classes (Pbside) (INEL) s = 7 ev PbPb s NN =.76 ev Preliminary s = 7 ev VM Mult. Evt. Classes imilarly to what was shown for Λ/π, the trends observed for and Pb are very similar Pythia 6 and 8 redicons also show strong disagreement with the observed trend for Ξ/π and Ω/π Comaring to thermal model redicons (HERMU/GI Heidelberg models), Ξ/π seems to rea the GC saturaon value but Ω/π stays below dn /dη η <.5 5

25 Results: and Pb scaled by INEL INEL / [h/π] system [h/π].5 ALICE Preliminary y <.5 s=7ev Pb s NN =5.eV /π /π Λ/π Λ/π Ξ/π Ξ/π Ω/π Ω/π he relave increase with mullicity is more ronounced for baryons with higher strangeness content.5 he observed increase seems to be strangeness related rather than baryon related since for rotons the rao remains constant u to the highest <N > robed.5 dn /dη η <.5 ALI PREL 9897 R.D. de ouza IMD 5 7 October 5 6

26 ummary Measurements of strange and strange hadrons have been erformed as a func@on of arged ar@cle density in collisions at s = 7 ev with the ALICE exeriment he sectra shae are observed to become harder as one selects on higher mullicity events he trend of Λ/K vs for different mullicity selecons observed in is similar to the corresonding observaons in Pb and Pb Pb Increase of yield raos (Λ/π, Ξ/π, Ω/π) with mullicity also follows the same trend observed in Pb Comarisons with redic@ons from Monte Carlo generators Pythia 6 and 8 show strong disagreement for all cases hank you for the attention! R.D. de ouza IMD 5 7 October 5 7

27 R.D. de ouza IMD 5 7 October 5 Backu

28 (backu) Mullicity elecon Classes VM Classes K and Λ Ξ Ω <dn /dη> η <.5 VM Classes <dn /dη> η <.5 %.9±.4±.64 %.9±.4±.64 5% 6.5±.±.5 5% 6.5±.±.5 VM Classes <dn /dη> η <.5 5% 7.47±.±.5 5 %.46±.±.5 5 %.46±.±.5 5%.5±.±.5 5%.5±.±.5 5 5%.48±.±.8 5 %.8±.±. % 8.45±<.±.5 4% 6.7±<.±. 4 5% 5.4±<.±.7 5 % 8.99±.±.7 5 % 8.99±.±.7 5% 6.6±<.±.9 5% 6.6±<.±.9 5 7%.9±<.±.4 5 7%.9±<.±.4 7 %.6±<.±. 7 %.6±<.±. 5 %.89±<.±.4 R.D. de ouza IMD 5 7 October 5

29 (backu) π and sectra N/dyd d /N evt π + +π, s=7 ev, VM Multilicity: 7% 57% (x ) 45% (x ) 4% (x ) 4 5 % (x ) 5% (x ) 6 7 5% (x ) 5% (x ) 8 9 5% (x ).% (x ).% (x ) ALICE Preliminary dn /dη =5. dn /dη =. N/dyd d /N evt , s=7 ev, VM Multilicity: 7% 57% (x ) 45% (x ) 4% (x ) 4 5 % (x ) 5% (x ) 6 7 5% (x ) 5% (x ) 8 9 5% (x ).% (x ).% (x ) ALICE Preliminary dn /dη =5. dn /dη =. Ratio to % Ratio to % ALI PREL ALI PREL R.D. de ouza IMD 5 7 October 5

30 (backu) φ/(π + +π ) vs mullicity ) +π + φ/(π. PbPb, s NN =.76 ev, ALICE, PRC 9, 469 (5) Pb, = 5. ev, ALICE reliminary.5, s NN s = 7 ev ALI PREL 9775 R.D. de ouza IMD 5 7 October 5 ALICE Preliminary, s = 7 ev + φ K +K, y <.5 VM Multilicity Event Classes Uncertainties: stat.(bars), sys.(box), uncorr.(shaded box) dn /dη η <.5 lab

31 (backu) Accetance Efficiency BR A.6.5 ALICE Performance s=7ev y <.5 BR A.4.5. ALICE Performance s=7ev y < K Λ Λ.5..5 Ξ + Ξ Ω + Ω ALI PERF ALI PERF R.D. de ouza IMD 5 7 October 5

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