Nuclear matter at HIRFL-CSR in LanzhouNuclear matter at HIRFL-CSR in Lanzhou

Zhigang XiaoZhigang XiaoDDepartment of Physics, Tsinghua Universityepartment of Physics, Tsinghua University

Conference on Strangeness in Quark MatterOct. 05-10, 2008, Tsinghua Uni., Beijing

Collaborators

THU: M. ZhangIMP : H. S. Xu, G. M. Jin, F. Fu, G. C. YongTexas A&M: B. A. Li SJTU: L. W. ChenGSI ： FOPI collaboration

Content

Introduction to HIRFL － CSR1 Machine and detector status

Nuclear matter at GeV/u regime Equation of state of asymmetric nuclear matter Softening of Esym() at supra-density from probe

Why HIRFL-CSR Stopping and compression in HIC More simulations for CSR energy regime

Summary

1. Heavy Ion Research Facility at Lanzhou—Cooling Storage Ring

HIRFL-CSR HIRFL-CSR ComplexComplex

Building 2#

Bu

ildin

g 6

#

CSRm

CSRe

SFC

SSCSFC: up to 10 AMeV

SSC: up to 100 AMeV

CSRm: 1.1 AGeV(12C6+), 2.8 GeV(p)

CSRe: 0.76 AGeV (12C6+)

NorthSFC – Sector Focusing Cyclotron

K ＝ 69 Ek(12C) = (0.5 － 17) MeV/u

。

SSC – Separated Sector Cyclotron

K ＝ 450 Ek(A/q=2) 110 MeV/u。

CSRm – Cooling Storage Ring main

• Ek(A/q=2) 1000 MeV/u

。

HIRFL-CSR PhotosHIRFL-CSR Photos

HIRFL-CSR HIRFL-CSR Research Research ProgramsPrograms

Nuclear Physics Nuclear spectroscopy, Super-Heavy Nuclide

(SHN), RIB physics Reaction dynamics and nuclear matter

Atomic Physics Highly Charged Ions, High Energy Density

Matter, Molecular & cluster beams

Material Science

Radio-biology & cancer therapy with heavy ions

Accelerator physics

Current beams at CSRCurrent beams at CSRIonsIons ：： 12C6 + ， 36Ar18+ ， 129Xe27+, 86Kr

Energy:Energy: 1 GeV/u for C & Ar in CSRm

Intensity:Intensity: 3.2 mA (1.61010) for C-7 MeV/u in CSRm

10 mA (7109) for C-600 MeV/u in CSRm

1.2 mA (4108) for Ar-368 MeV/u in CSRm

0.5 mA (1108) for Xe-235 MeV/u in CSRm

15 mA (8109) for C-660 MeV/u in CSRe

~1108 for Kr-450 MeV/u in CSRm

Experiment:Experiment: RIB from RIBLL2, test with isochronous mode in CSRe , ∆M/M~10-6

Slow-extraction:Slow-extraction: 1.2 s for Ar-368MeV/u from CSRm

3.0 s for 12C4+-300 MeV/u from CSRm

ETE Phase IETE Phase I(External Target Experiment – Phase I)(External Target Experiment – Phase I)

detectors: 4 segmented C

• MWDC: 6, with conventional technique lover detectors

• ToF Wall: 3, 2 layers of BC408 bars, 30 bars/layer, readout from both ends with PMT (R7525)

• Neutron Wall: 14 layers, 18 paddles/layer, readout from both ends with PMT (R7724); BC408 only for the first two layers, sampling type (BC408+Fe) for the others

ETE Phase IIETE Phase II

New DetectorsNew Detectors• -ball

(CsI(Tl) array•MWPC (inside dipole)• Si-strip array (inside dipole)• TPC? (at target region)

Possible PhysicsPossible Physics• For RIB Physics• For EoS of asymmetry nuclear matter• For high baryon density matter

To be constructed within 4 years if approved.

Key part！！

Content

Introduction to HIRFL － CSR1 Machine and detector status

Nuclear matter at GeV/u regime Equation of state of asymmetric nuclear matter Softening of Esym() at supra-density from probe

Why HIRFL-CSR Stopping and compression in HIC More simulations for CSR energy regime

Summary

1. Heavy Ion Research Facility at Lanzhou—Cooling Storage Ring

Equation of State of nuclear matter Equation of State of nuclear matter

Consistence Consistence Maintained at Maintained at 00

Unknown at Unknown at > > 00

...

3...

16218)()(),( 23

22

sym2

0 LEaEEE symV

:Compressibility EsymZN

ZN

~1 GeV/u

Probes to EProbes to Esymsym(() II: high density) II: high density

B. A. Li PRC71 (2005)014608

Probe 2: Probe 2: --//++ ratio ratio

Complete set of Complete set of multiplicity multiplicity

W. Reisdorf et al. for FOPI collaboration NPA 781(2007) 459

Asymmetric energy at high densityAsymmetric energy at high density ： ： little known little known

IBUU04:B. A. Li Phys. Rev. Lett. 88, 192701 (2002)L. W. Chen et al., PRC 76, 054316

G.C.Yong et al., PRC73(2006)034603

B.-A. Li, PRC 69 (2004) 064602

C. B. Das, S. Das Gupta, C. Gale, B. A. Li PRC67(2003) 034611

Revisit Revisit and its relevance of and its relevance of EEsymsym(())

Multiplicity Multiplicity

Multiplicity reproduced by tMultiplicity reproduced by the model, But shows insignihe model, But shows insignificant sensitivity on the Eficant sensitivity on the Esymsym

(().).

EEbb>0.6GeV/u: >0.6GeV/u:

Undistinguishable Undistinguishable

EEbb<=0.6GeV/u: <=0.6GeV/u:

Soft ESoft Esymsym seems to be f seems to be f

avored.avored.

R(R(--//++) vs E) vs Ebeambeam

Softening of Esym() at supra-normal density

High density effectHigh density effect

High density effect is the main contribution High density effect is the main contribution

Switch x at <0

Switch x at >0

Density profile Density profile

High density achieved in the central region, where a larger N/Z asymmetry is experienced with a softer Esym().

Higher R(-/+) .

X=1 soft

X=-1 hard

Content

Introduction to HIRFL － CSR1 Machine and detector status

Nuclear matter at GeV/u regime Equation of state of asymmetric nuclear matter Softening of Esym() at supra-density from probe

Why HIRFL-CSR Stopping and compression in HIC More simulations for CSR energy regime

Summary

1. Heavy Ion Research Facility at Lanzhou—Cooling Storage Ring

Sensitivity vs ESensitivity vs Ebeambeam

beam energy beam energy

stopping stopping

sensitivity sensitivity

Measurement of pion emissions at CSR energy range (<1GeV Measurement of pion emissions at CSR energy range (<1GeV for HI) may helps to resolve the Efor HI) may helps to resolve the Esymsym(()!)!

Stopping Transverse/Longitudinal symmetry

FOPI collaboration et al., In preparation

Ni+Ni Ni+Ni

Pb+Pb Pb+Pb

EEbb=0.4,0.8 and 1.2 GeV/u=0.4,0.8 and 1.2 GeV/u

Normalized to sameNormalized to same

system sizesystem size

Stopping hierarchy:Stopping hierarchy:

Higher EHigher Ebeambeam

less stopping;less stopping;

Lighter systemLighter system

less stopping;less stopping;

Heavier massHeavier mass

less stopping;less stopping;FOPI collaboration et al., In preparation

Pb+Pb vs. Ni+Ni

Stopping Stopping vs.vs. compression/pressure compression/pressure

More CompressedMore Compressed

Larger signal Larger signal More sensitive on EOS More sensitive on EOS More StoppingMore Stopping

F. Fu, et al. PLB666(2008)359

Stopping vs Density gainStopping vs Density gain

Less compressionLess compression

Lower gainLower gain

for baryon densityfor baryon density

Less StoppingLess Stopping

F. Fu, Z. G. Xiao et al., PLB666(2008)359

Sensitivity vs System sizeSensitivity vs System size

The increasing sensitivity of pion probe on Esym() is evident when passing from Ca+Ca to Au+Au

we report the status of the new facility CSR at Lanzhou which will be able to make rather contributions in nuclear EOS study, particularly on Esym() at high density. The sub-GeV/u energies, for the maximum nuclear stopping verified experimentally, are advantageous for converting the beam energy to compression up to 2~30 .

Within an isospin dependent transport framework, the most recen

t and complete data set an partial constraint on Esym(). For the first time we observed a softening of Esym() at supra-density, which might have many astrophysical indications. Further simulations show that at CSR energies, the sensitivity of the probe on Esym

() increases with decreasing the beam energy or increasing the system size.

SummarySummary

The fate of Spinosaurid …The fate of Spinosaurid …

For about 50 yrs Spinosaurid has been vegetarian, now it’s a carnivore.

Imagine what it’ll be in the next 50 yrs, 100 yrs, …?

P.C. Sereno et al. Science, Nov. 13, 1298(1998). (Spinosaurid)

Thank you!Thank you!

Backup slides start here:Backup slides start here:

Not likely distinNot likely distinguishable! guishable!

Some advantages at CSR energy regimeSome advantages at CSR energy regime

Density as high as 2~30 , varying rapidly with beam energy;

Maximum stopping, maximum sensitivity on the Esym();

More for s,

Most copious produced, copious information of isospin effect; NOT influenced by the problem of clustering in transport.

……

Sensitivity vs System sizeSensitivity vs System size

Larger colliding systeLarger colliding system more compressed am more compressed and the sensitivity on End the sensitivity on E

symsym(() increases with sy) increases with sy

stem size. stem size.

Stopping in IQMD (II)Stopping in IQMD (II)

Above 400 MeV/u, for the Above 400 MeV/u, for the heavy system, flow and stoheavy system, flow and stopping are close to datapping are close to data

19321932 中子发现后，就有中子星假设，中子发现后，就有中子星假设， 3434 年年 BaadeBaade 等人就预言这种星体在超新星爆发后可能产生，等人就预言这种星体在超新星爆发后可能产生，19671967 年年 BellBell 和和 HewishHewish 等人发现第一颗辐射脉冲星，等人发现第一颗辐射脉冲星， HulseHulse 和和 TaylorTaylor 等便发现第一颗双星体，其等便发现第一颗双星体，其中便有一颗中子星存在。中便有一颗中子星存在。

7070 年代年代 QCDQCD 的渐进自由性质提出以后，人们便意识到在高密的中子星核心内可能存在至夸克物质的渐进自由性质提出以后，人们便意识到在高密的中子星核心内可能存在至夸克物质的相变。的相变。 19841984 年年 WittenWitten 就提出由就提出由 uu 、、 dd 、、 ss 等组成的奇异夸克星体可能存在，即夸克星。等组成的奇异夸克星体可能存在，即夸克星。

中子星半径约中子星半径约 1010 公里，质量公里，质量 1~2M1~2M 早期通过中微子发射冷却，而后期通过表面光子发射致冷。对早期通过中微子发射冷却，而后期通过表面光子发射致冷。对脉冲星而言， 转动周期在脉冲星而言， 转动周期在 msms 量级。量级。

表面壳层由重核与简并电子构成。向中心方向压力和密度增加，电子可能被核俘获，同时中子游离表面壳层由重核与简并电子构成。向中心方向压力和密度增加，电子可能被核俘获，同时中子游离于重核之外，因此系统逐渐向于重核之外，因此系统逐渐向 AA ＋＋ nn ＋＋ ee 这样的体系过度。最后，重核解体为中子、质子和电子体这样的体系过度。最后，重核解体为中子、质子和电子体系。在密度大于系。在密度大于 1n1nss 时，时，可能存在可能存在 (( 由于密度增加导致由于密度增加导致 ee 化学势最终大于化学势最终大于的质量，其的质量，其 FermiFermi 面变面变得不再稳定， 得不再稳定， ee 向向的衰变可能产生的衰变可能产生 )) 。当密度增至数倍。当密度增至数倍 nnss 的时，其它奇异的成分，如超子的时，其它奇异的成分，如超子 (( 同同理理 )) ，， KK 凝聚和解禁闭夸克等可能存在。凝聚和解禁闭夸克等可能存在。

Neutron Star Neutron Star NS with

quark core

Strang

e Qua

rk S

tar

NS with Meson

condensation NS with

hype

ron c

ore

0 - K-

n p e

n p e

n p e

u d s eu d s

Outer (A+e)

& Inner (A+n+e)

crust

R ~10km

M-R relation of Neutron M-R relation of Neutron StarStar

最大质量与最大质量与 EOSEOS 相关，图中曲线为相关，图中曲线为Mmax>1.44Mmax>1.44 的的 EOSEOS

通常认为，通常认为， Stiff EOS Stiff EOS 意味着大的最意味着大的最大质量和大的半径。对于大质量和大的半径。对于 >Msolar>Msolar的星体来说，只有充分的星体来说，只有充分 softsoft 的的 EOSEOS才可能有才可能有 RR<12km<12km最大的质量（不是某个星体的质最大的质量（不是某个星体的质量）为高密量）为高密 EOSEOS 性质控制。核子之性质控制。核子之外的自由度的引入将会使外的自由度的引入将会使 EOSEOS 变软；变软；只是观测到的已知的最大星体只是观测到的已知的最大星体 1.441.44MsMs 太小，不足以确定高密核物质中太小，不足以确定高密核物质中的组分和星体的结构信息。的组分和星体的结构信息。

另一方面，另一方面， NSNS 半径则主要取决于半径则主要取决于 nnss 附近的核力性质，尤其是对称能项附近的核力性质，尤其是对称能项的密度依赖行为。这主要是因为的密度依赖行为。这主要是因为 NSNS的半径与内部压力（的半径与内部压力（ 1.51.5 ～～ 3ns3ns ））之间的关系（之间的关系（ RP^RP^ －－ 1/4=const1/4=const ）。）。在 在 nsns 附近，附近， PP 与与 KK ，， K’K’ 和和 EsymEsym有关，但是在高密度时，有关，但是在高密度时， KK 和和 K’K’ 的的贡献几乎抵消，剩下的仅仅是贡献几乎抵消，剩下的仅仅是 EsymEsym的密度依赖行为。的密度依赖行为。

Z. G. Xiao, R. J. Hu et al., PLB 639 (2006) 436

Probe 5Probe 5 ：： IMF correlation functionIMF correlation function

Waiting for transport studiesWaiting for transport studies

M-R relation of Neutron M-R relation of Neutron StarStar

除了除了 MmaxMmax 和和 RR 之外，之外， NSNS热学性质的观测也是我们了解强相互作用物质性质的途径。热学性质的观测也是我们了解强相互作用物质性质的途径。现在人们意识到，现在人们意识到， EsymEsym （（ rhorho ）对于中微子冷却率起关键作用，这不仅是因为）对于中微子冷却率起关键作用，这不仅是因为 EsyEsymm 控制冷却率，还决定了在何种密度下，奇异子、超子或凝聚现象可以发生。这些奇控制冷却率，还决定了在何种密度下，奇异子、超子或凝聚现象可以发生。这些奇异现象的出现会使得冷却率加快。异现象的出现会使得冷却率加快。

Core-crust transition controlled by Esym at high densityCore-crust transition controlled by Esym at high density

Critical density for condensation depends on the symmetry energy of nucleonic mattCritical density for condensation depends on the symmetry energy of nucleonic matterer

CrustCrust中子星有一个固态的中子星有一个固态的 CrustCrust ，，包绕着一个包绕着一个 uniformuniform 的液态物的液态物质，后者可视为含有很少量质质，后者可视为含有很少量质子的中子物质。这个子的中子物质。这个 CrustCrust具具有一定的观测效应，但是在计有一定的观测效应，但是在计算算 curstcurst 的转动惯量分量时，的转动惯量分量时，需要知道何时发生了从需要知道何时发生了从 nucleinuclei致致 uniform matteruniform matter 的相变，这的相变，这需要需要 EsymEsym 信息。信息。在忽略表面和在忽略表面和 CoulombCoulomb 效应效应的近似下，这可以考虑为纯的近似下，这可以考虑为纯 npnpee 物质变得不稳定产生两相物质变得不稳定产生两相（原子核和核子海）分离的临（原子核和核子海）分离的临界密度。界密度。

1932 中子发现 , 34 ，中子星预言1967,Bell 和 Hewish ， 1st pulsarHulse 和 Taylor ， 1st 双星体70 年代， QCD 的渐进自由性质1984 ， Witten ，夸克星可能性

R ～ 10km ， W 1~2M ，对脉冲星而言， 转动周期在 ms 量级。早期通过中微子发射冷却，后期通过表面光子发射致冷。

表面壳层：重核与简并电子向 A ＋ n ＋ e 体系过度。最后，重核解体为中子、质子和电子体系。>1ns 时，可能存在。

>~3ns 的时，其它奇异的成分，如超子， K凝聚和解禁闭夸克等可能存在。

Clustering: system size dependenceClustering: system size dependence

1 Heavier system favors more clustering.2 Lower Eb (slower/longer expansion ) favors clustering.3 Nature is purely “coalescence”? If not, what else?

斜率 dN/dA(y0) = C(y0)*exp(sA)

5 What cause different y0 dependence behavior in light and heavy system?6 Correlation between stopping and clustering?

Clustering in IQMD (I)Clustering in IQMD (I)

Yield and EOS Yield and EOS

4 Sensitivity on EOS Helps NOT to resolve EOS!

dN/dY in IQMD dN/dY in IQMD

Clustering physics is Clustering physics is enriched in this regime, enriched in this regime, but not fully understood; but not fully understood; transport does not transport does not repeat the data in the repeat the data in the highly transparent highly transparent

systems or species!systems or species!

Again, due to the large Again, due to the large discrepancy between discrepancy between the yield in the model the yield in the model and in data, EOS and in data, EOS constraint is unlikely constraint is unlikely conclusive.conclusive.

HIRFL-CSR Experiments on HIRFL-CSR Experiments on Nuclear PhysicsNuclear Physics

Building 2#

Bu

ildin

g 6

#

CSRm

CSRe

SFC

SSCSFC: up to 10 AMeV

SSC: up to 100 AMeV

CSRm: 1.1 AGeV(12C6+), 2.8 GeV(p)

CSRe: 0.76 AGeV (12C6+)

NorthLocation ILocation I Nuclear spectroscopy

• drip-line nuclei, Nuclear chemistry, SHN

。

Location IILocation II• Nuclear spectroscopy

• H.I. collision dynamics

• RIB Physics

• drip-line nuclei & SHN

。

Building 2#

Bu

ildin

g 6

#

CSRm

CSRe

SFC

SSCSFC: up to 10 AMeV

SSC: up to 100 AMeV

CSRm: 1.1 AGeV(12C6+), 2.8 GeV(p)

CSRe: 0.76 AGeV (12C6+)

NorthLocation III (within 2~3 years)Location III (within 2~3 years)• RIB Physics

• EoS of Asymmetric nuclear matter

• High baryon density nuclear matter

Location IV (on-Location IV (on-going)going)• mass measurement

• decay spectroscopy

Location V (within 1year)Location V (within 1year)• Spallation

•Application

Location VI (planned)Location VI (planned)• Hadron Spectroscopy

• Isospin Physics

• Spin physics

HIRFL-CSR Experiments on HIRFL-CSR Experiments on Nuclear PhysicsNuclear Physics

Beam signal for slow extraction in CSRmBeam signal for slow extraction in CSRm2008.01.10 15:00

36Ar18+-368MeV/u36Ar18+-368MeV/u

Slow-extractionSlow-extractionSuccessSuccess

Spill length: 1.2sMain frequency: 50Hz

EEsymsym(() controls NS structural properties) controls NS structural properties Proton fractionProton fraction M-R relationM-R relation c c for D-Urca for D-Urca Transition densityTransition density …… …… Phy. Rep. 442(2007) 109; NPA777(2006)479Phy. Rep. 442(2007) 109; NPA777(2006)479PRC76(2007),025801; PRC75(2007) 015801PRC76(2007),025801; PRC75(2007) 015801PRC74 (2006),035802PRC74 (2006),035802Astro. J. 676 (2008) 1170Astro. J. 676 (2008) 1170Phy. Rep. 411(2005) 325Phy. Rep. 411(2005) 325

B. A. Li et al., PLB 642, 436 (2006)

Probes to EProbes to Esymsym(() I: low density) I: low densityIsospin diffusion Isospin diffusion Neutron Skin in Neutron Skin in 208208PbPb

Fast nucleon emissionFast nucleon emission Isospin scaling Isospin scaling

Asy-soft at normal or sub-normal density.Asy-soft at normal or sub-normal density.

05.1~69.0

0

6.31)(

symE

MassMass Measurement of RIBs in CSRe2007.12.07

Isochronous Mode: = tr = 1.395, ToF

2

22(1 )

1 ( / )

/t

rev

rev t

df dv d m q

f v m q

Slow extraction for Slow extraction for 1212CC4+4+-300MeV/u-300MeV/u in CSRmin CSRm2008.05.21 03:31 From Scintillation Crystal

Monitor

Probes to EProbes to Esymsym(() II: high density) II: high density

Probe 1: Probe 1:

n/p differential flow:n/p differential flow:

Asy-Soft Asy-Soft Smaller diffe Smaller differential flow rential flow

B. A. Li et al., PRL88 (2002) 192701

Soft

Hard

Soft

Hard