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Abstract Two-particle correlations with $$\textrm{K}^{0}_\mathrm{{S}}$$ K S 0 , $$\Lambda $$ Λ / $$\overline{\Lambda }$$ Λ ¯ , and charged hadrons as trigger particles in the transverse momentum range $$8{<}p_{{\textrm{T}},{\textrm{trig}}}{<}16$$ 8 < p T , trig < 16 GeV/ $$c$$ c , and associated charged particles within $$1{<}p_{{\textrm{T}},{\textrm{assoc}}}{<}8$$ 1 < p T , assoc < 8 GeV/ $$c$$ c , are studied at midrapidity in pp and central Pb–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision $$\sqrt{s_{\textrm{NN}}}~=~5.02$$ s NN = 5.02 TeV with the ALICE detector at the LHC. After subtracting the contributions of the flow background, the per-trigger yields are extracted on both the near and away sides, and the ratio in Pb–Pb collisions with respect to pp collisions ( $$I_{\textrm{AA}}$$ I AA ) is computed. The per-trigger yield in Pb–Pb collisions on the away side is strongly suppressed to the level of $$I_{\textrm{AA}}$$ I AA $$\approx 0.6$$ ≈ 0.6 for $$p_{{\textrm{T}},{\textrm{assoc}}}>3$$ p T , assoc > 3 GeV/ $$c$$ c as expected from strong in-medium energy loss, while an enhancement develops at low $$p_{{\textrm{T}},{\textrm{assoc}}}$$ p T , assoc on both the near and away sides, reaching $$I_{\textrm{AA}}$$ I AA $$\approx 1.8$$ ≈ 1.8 and 2.7 respectively. These findings are in good agreement with previous ALICE measurements from two-particle correlations triggered by neutral pions ( $$\pi ^{0}$$ π 0 –h) and charged hadrons (h–h) in Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}}~=~2.76$$ s NN = 2.76 TeV. Moreover, the correlations with $$\textrm{K}^{0}_\mathrm{{S}}$$ K S 0 mesons and $$\Lambda $$ Λ / $$\overline{\Lambda }$$ Λ ¯ baryons as trigger particles are compared to those of inclusive charged hadrons. The results are compared with the predictions of Monte Carlo models.
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Constraining the Chiral Magnetic Effect with charge-dependent azimuthal correlations in Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 2.76 and 5.02 TeV
A bstract Systematic studies of charge-dependent two- and three-particle correlations in Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 2.76 and 5.02 TeV used to probe the Chiral Magnetic Effect (CME) are presented. These measurements are performed for charged particles in the pseudorapidity ( η ) and transverse momentum ( p T ) ranges | η | < 0 . 8 and 0 . 2 < p T < 5 GeV/ c . A significant charge-dependent signal that becomes more pronounced for peripheral collisions is reported for the CME-sensitive correlators γ 1, 1 = 〈cos( φ α + φ β − 2Ψ 2 )〉 and γ 1, − 3 = 〈cos( φ α − 3 φ β + 2Ψ 2 )〉. The results are used to estimate the contribution of background effects, associated with local charge conservation coupled to anisotropic flow modulations, to measurements of the CME. A blast-wave parametrisation that incorporates local charge conservation tuned to reproduce the centrality dependent background effects is not able to fully describe the measured γ 1 , 1 . Finally, the charge and centrality dependence of mixed-harmonics three-particle correlations, of the form γ 1, 2 = 〈cos( φ α + 2 φ β − 3Ψ 3 )〉, which are insensitive to the CME signal, verify again that background contributions dominate the measurement of γ 1 , 1 .
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- PAR ID:
- 10278021
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Journal of High Energy Physics
- Volume:
- 2020
- Issue:
- 9
- ISSN:
- 1029-8479
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/JHEP09(2020)160
