AMPT Phenomenology with Chiral Effect

Transcription

1 AMPT Phenomenology with Chiral Effect Guo-Liang Ma Shanghai Institute of Applied Physics, Chinese Academy of Sciences This work is in collaboration with Xu-Guang Huang, Yu-Gang Ma, Qi-Ye Shou, and Bin Zhang. 1

2 Outline Introduction AMPT results on CME [1] G.-L. Ma and B. Zhang, PLB 700 (2011) 39 [arxiv: ]. [2] Q. -Y. Shou, G.-L. Ma and Y. -G. Ma, PRC 90 (2014) [arxiv: ]. AMPT results on CMW [3] G.-L. Ma, PLB 735 (2014) 383 [arxiv: ]. AMPT results on CESE [4] G.-L. Ma and X.-G. Huang, arxiv: Summary 2

3 chiral magnetic effect=> dipole charge separation dipole PRL 103, (2009) RHIC data are consistent with the CME expectation that charges could be distributed asymmetrically w.r.t reaction plane, i.e. dipole charge separation. Non-flow/non-parity effects: largely cancel out Directed flow: vanishes if measured in a symmetric rapidity range P-even quantity: still sensitive to charge separation 3

4 chiral magnetic wave =>quadrupole charge separation Chiral magnetic wave Yannis Burnier, Dmitri Kharzeev, Jinfeng Liao, Ho-Ung Yee, PRL 107, (2011) quadrupole STAR preliminary STAR preliminary RHIC-STAR data are consistent with the CMW expectation, i.e. quadrupole charge separation 4

5 Charge asymmetry slope r of pion v2 RHIC-STAR data can be described by the CMW expectations with different CMW duration times. UrQMD can not reproduce the slopes r. 5

6 chiral electric separation effect => quadrupole charge separation X.G.Huang and J.F.Liao, PRL 110, (2013) Chiral electric separation effect (CESE) : E-field induces an axial current, i.e. a chirality separation. CESE+CME+in-plane CSE=>a new type of quadrupole charge separation in Cu+Au. How to observe CESE experimentally? 6

7 A multiphase transport (AMPT) model Melting AMPT Model (1) initial condition (2) parton cascade [2<->2 elastic collisions] (3) hadronization (4) hadronic rescatterings Z. -W. Lin et al., PRC 72 (2005) Resonance decays only are employed to ensure charge conservation, without hadron rescatterings. 7

8 (I)AMPT results on CME [1] G.-L. Ma and B. Zhang, PLB 700 (2011) 39 [arxiv: ]. [2] Q. -Y. Shou, G.-L. Ma and Y. -G. Ma, PRC 90 (2014) [arxiv: ]. 8

9 The AMPT model with dipole charge separation (1) Introduction G.-L. Ma, B. Zhang, PLB 700 (2011) 39 dipole dipole charge separation u u u u We include initial dipole charge separation mechanism into AMPT model. We switch the p y values of a percentage of the downward moving u quarks with those of the upward moving u-bar quarks, and likewise for d-bar and d quarks, where the percentage is a relative ratio with respect to the total number of quarks. We focus on final state effects on the charge separation, including parton cascade, hadronization, resonance decays after B and E vanish quickly. 9

10 AMPT results on <cos(φα+φβ)> G.-L. Ma, B. Zhang, PLB 700 (2011) 39 An initial charge separation ~10% can describe same-charge data in the presence of strong final state interactions. But ~10% only can describe opposite-charge correlation for 60-70%. From a percentage of charge separation of 10% in the beginning 1-2% percentage at the end. 10

11 CME vs trans. mom. conservation The AMPT result without initial charge separation is very close to the expectation of trans. mom. conservation [dashed: <cos(φ α +φ β )>=-v 2 /N]. TMC can partly account for data, and an initial 10% dipole charge separation are needed.=> CME+pT conservation ~ experimental data 11

12 AMPT results on Δη and pt dependences of <cos(φα+φβ)> G.-L. Ma, B. Zhang, PLB 700 (2011) 39 =(pt α +pt β )/2 AMPT results with an initial charge separation of 10% can describe Δη and pt dependences of same-charge data. AMPT results without initial charge separation are consistent with the expectation from TMC [dashed: <cos(φ α +φ β )> p + n (n=2~3)], however n=2.2( for 0%) n=1.5(for 10%). 12

13 The AMPT model with local dipole charge separation (1) Introduction dipole local dipole charge separation Q. -Y. Shou, G.-L. Ma and Y. -G. Ma, PRC 90 (2014) We include initial local dipole charge separation mechanism into AMPT model. Within a same metastable domain, we switch the p y values of the downward moving u quarks with those of the upward moving u-bar quarks, and likewise for d-bar and d quarks. We compare the results from local dipole charge separation with the previous global case and exp. data. We aim to extract the information about the properties of metastable domains, such as number and size of domains. 13

14 <cos(φα+φβ)> from AMPT with local dipole charge separation Q. -Y. Shou, G.-L. Ma and Y. -G. Ma, PRC 90 (2014) A domain-based charge separation improves the description of opposite-charge correlation. 14

15 How many domains Q. -Y. Shou, G.-L. Ma and Y. -G. Ma, PRC 90 (2014) The domain production rate is consistent with charge separation percentage. We use all possible domains for each centrality bin. It is possible to improve it by adjusting the centrality dependence of domain rate. 15

16 How big the total volume of domains Q. -Y. Shou, G.-L. Ma and Y. -G. Ma, PRC 90 (2014) The size and number of metastable domains should be relatively small in the early stage of QGP. 16

17 (II)AMPT results on CMW G.-L. Ma, PLB 735 (2014) 383 [arxiv: ]. 17

18 The AMPT model with quadrupole charge separation (1) Introduction G.-L. Ma, PLB 735 (2014) 383 quadrupole quadrupole charge separation How to include initial quadrupole charge separation into the AMPT model: I switch the positions (x,y,z) of a percentage of the small- y u quarks with those of large- y u-bar quarks, and likewise for d-bar and d quarks for Ach>-0.01 events; A contrary manner for Ach<-0.01 events. The goal is to learn some properties of chiral magnetic wave through how final charge asymmetry of pion v2 depends on the quadrupole percentage after B and E vanish. 18

19 Initial charge quadrupole distribution G.-L. Ma, PLB 735 (2014) 383 Yannis Burnier, Dmitri Kharzeev, Jinfeng Liao, Ho-Ung Yee,PRL 107, (2011) Initial partonic net charge distribution changes with quadrupole percentage. 19

20 Charge asymmetry of pion v2 G.-L. Ma, PLB 735 (2014) 383 The Ach asymmetry between pion+/- v2 appears for a non-zero initial charge quadrupole. 20

21 Δv2 vs Ach G.-L. Ma, PLB 735 (2014) 383 No charge asymmetry of pion v2 for 0%. Δv2 increases with Ach for non-zero percentages. Δv2 increases faster with larger percentage. 21

22 Stage evolution for charge asymmetry of v2 G.-L. Ma, PLB 735 (2014) 383 r= / r= / r= / r= / exp. data: r= / The slope r is around zero initially. The slope r appears after parton cascade. The slope r increases after coalescence. The slope r is largely weaken due to resonance decays. 22

23 A helpful constraint on CMW G.-L. Ma, PLB 735 (2014) 383 0% <1% 1-2% 1-2% 2-3% 2-3%? 3-4%?% centrality bin 0-10% 10-20% 20-30% 30-40% 40-50% 50-60% 60-70% 70-80% initial quad. perc. 0% <1% 1-2% 1-2% 2-3% 2-3% 3-4%?% It gives a constraint (<4%) to the centrality dependence of initial quadrupole percentage. 23

24 (III)AMPT results on CESE G.-L. Ma and X.-G. Huang, arxiv:

25 The AMPT model with CESE charge separation (1) Introduction y E G.-L. Ma and X.-G. Huang, arxiv: Au Cu x CESE+CME+in-pla CSE charge separation quadrupole We include different kinds of initial charge separations, e.g. CESE+CME +in-plane CSE, into the Cu+Au initial condition of the AMPT model. To observe the embedded effects in the final state, what are possible observables? 25

26 The different inputs of initial charge separation (1) Introduction Cu+Au 200 GeV G.-L. Ma and X.-G. Huang, arxiv: Cu+Cu 200 GeV (a) Normal (b) CME (c) in-plane CSE (d) CESE+CME+in-plane CSE (e) CESE+2xCME+in-plane CSE (f) CESE+CME+2xin-plane CSE Six different kinds of initial charge separations as the Cu+Au initial conditions. b-dependent initial charge separation percentage f% is taken by fitting Cu+Cu data, i.e. f=1.56b/fm. 26

27 <cos(ϕa+ϕβ)> from different initial chiral effects G.-L. Ma and X.-G. Huang, arxiv: <cos(ϕa+ϕβ)> is a sensitive probe for CME and in-plane CSE. In-plane CSE reverses the sign of the signal of CME. <cos(ϕa+ϕβ)> is not sensitive to CESE. 27

28 1st proposed CESE observable: <cos[2(ϕa+ϕβ)]> E y G.-L. Ma and X.-G. Huang, arxiv: Au ψc Cu -ψc x ζaβ=<cos[2(ϕa+ϕβ)]> For CME or in-plane CSE: ζopp=ζsame~<cos(4ψd)>, Δζ=ζopp-ζsame~0 For CESE: ζopp~1 and ζsame~ <cos(4ψc)>, Δζ=1-<cos(4ψc)> Δζ=ζopp-ζsame is a clear signal for the CESE. Once CESE happens, Δζ increases from central to peripheral Cu+Au collisions. 28

29 2nd proposed CESE observable: <Ψ2 + -Ψ2 - > E y G.-L. Ma and X.-G. Huang, arxiv: Au ψc Cu -ψc x Ψn +/- +/- +/- [Ψ2 + (Ψ2 - ) is the 2nd event plane angle reconstructed by final positivecharge (negative-charge) hadrons.] Once the CESE happens, <Ψ2 + -Ψ2 - >~2<ψc> increases from central to peripheral centrality bin. 29

30 Summary Final state interactions reduce the CME signal, the percentage of initial dipole charge separation could be large~10%. Domain-based AMPT results indicates that the size and number of metastable domains should be relatively small. The slope r of charge asymmetry of pion v2 is sensitive to the percentage of the initial quadrupole charge separation, which gives a helpful constraint (<4%) to the CMW effect. Cu+Au provides us a good chance to disentangle CESE and other chiral effects through the proposed observables. 30

31 Thanks for your attention! 31