電磁プローブ(フォトン＆レプトン対)⼭⼝頼⼈
理研BNLセンター
Heavy Ion Café & Pub合同研究会@名古屋⼤at RHIC√ show that dNch /dy at s = 200 AGeV is indeed by a factor of 2 larger than at
SPS ( s = 17 AGeV), but, surprisingly, the HBT source radii do not change much [ 24].
Although hydrodynamic simulations are currently not able to explain this feature, it canbe easily incorporated in a suitable fireball parameterization of the expansion. We have
• 重イオン衝突でできる媒質に対して透過的
employed such a phenomenologically improved description to assess the effect on dilep• spectra.
特にQGPからの熱放射：熱光⼦
tonIn addition we have also incorporated antibaryon number conservation until
thermalüfreezeout
as delineated in Sect. 3.1. The resulting low-mass spectra are compared
温度が⾼いほど⼤きな放出レート
to the earlierof ref. [ 15] in Fig. 7. As to be expected, the reduced fireball−prediction
QGP初期からの⼤きな寄与を期待(低横運動量領域)
lifetime decreases the hadron gas yield-E/T
somewhat [ 15], but, more importantly, the imü
スペクトルの傾き(~e)からQGP温度測定
proved hadro-chemistry reinforces baryonic effects in terms of resonance broadening and− QGPライフタイムや温度変化を考慮する必要あり
low-mass enhancement.

フォトン & レプトン対• カイラル対称性回復によるベクターメソンの質量変化
ü 低質量電⼦対のcontinuum成分Central Au+Au s1/2=200AGeV

10-1

thermal:eDecay photons(p0→g+g, h→g+g, …)-2

free ρ+ω+φ (chem eq)
free ρ+ω+φ (off-eq)
in-med. ρ+ω+φ (chem eq)
hard:
in-med. ρ+ω+φ (off-eq)

-3

0.2

0.3

0.4

0.5

0.60.7

Mee [GeV]

0.80.9<Nch>=800

Cocktail
Thermal (eq)Thermal (off)Drell-Yan
Open Charm-510- Eg /T-6101pTn
1.0-710210<Nch>=800|yee|<0.35

Central Au+Au
1/2
s =200AGeV(d N/dMdy)/<Nch> [GeV ]-1-1(dNee/dM) [GeV ]101.1e-8100pt >0.2GeV|ye|<0.35

0.5

R.Rap, nucl-th/0204003

11.5

Mee [GeV]

22.5

熱光⼦：低横運動量直接光⼦

Direct photon
v2 puzzle
QM前の理解：DIRECT
PHOTONPUZZLE

Difficult for thelarge low pT yie

FireballSemi-QGP
w.o viscous
PHSD

Each theory curve has
vn is the weighted• 期待通りの⼤きな収量＆予期していなかった⼤きなv
2multiple contributing
average of source vn’sü ⼤きな収量 →
温度の⾼いearlystageからの寄与？
directphoton sources
Need a large
amount of photon proü ⼤きなv2 → フローが発達したlatestageからの寄与？
late in the collision after the anis
→ 新たな光⼦源の導⼊：
pressure
gradients have develo
Photon emissions at 1)Feb.Glasma& 2) meson
10, 2017
Sarah Campbellproduction,1) PHOTONS FROM GLASMA• Bottom-up thermalization scenario (丹治さんの発表)
R. Baier et al. / Physics Letters B 539 (2002) 46–52
ü 前熱平衡状態＝Glasmaからの放射を含む計算
R.Baier et al., Phys. Lett. B 539, 46 (2002)(8)

ch that xG(x, Q2 ) ≃ 2
he reference energy ofrees with various gluonin [23], and with then obtained from HERA
with Q2 .
onstant is(9)for Nc = 3; we takei.

with the above choicesii.
finds for central Au–Au= 130 GeV), taking foriii.
0) ≃ 0.63 GeV2 , usingiiiiiiHardFig. 1. gluon
Characteristicscatterings
momentum scales for the “bottom-up” scenario.
Softgluon bathHeat-up by remaining hard gluonsPHOTONSFROM scenario
GLASMABottom-up1)
scenariovs. Early-hydro• Bottom-up thermalization scenario (丹治さんの発表)ü 前熱平衡状態＝Glasmaからの放射を含む計算

Bottom-up
Early-Hydro

QGP lifetime

QGP lifetime• QGP@LHC
energyはより⻑いLifetime¾ Bottom-up thermalization
scenario:
Glasma (i), (ii), (iii) + Thermal ()ü RHIC energyではGlasmaからの放射の割合が増加üHydroPeripheral
collisionについても同様¾
scenario thatassumes early-thermalization:
Early-hydro () + Thermal ()1) PHOTONS FROM GLASMA

Bottom-up scenario vs. Early-hydroscenario
Bottom-up
scenario vs. Early-h• Bottom-up thermalization scenario (丹治さんの発表)ü 前熱平衡状態＝Glasmaからの放射を含む計算• Glasmaの光⼦⽣成率に強いQs2依存性
For a larger
the saturation
scale (For this value of the saturation scale (for thevalue
RHICofmost
central collision),ütwoSmallQs:give
Early-Hydro
bottom-up thermalization scenario gives
thescenarios
the comparablescenarioとconsistent
photontheyields.
ü Large Qs: Glasmaからのより⼤きな寄与
→For
⼤きなv
larger valueof the saturation scale…
2を作る機構を別に⽤意する必要あり

otonemission2) PHOTONSAT MESON PRODUCTION

Numerical resultdel• ReCombination model + photon emission (板倉さんの発表)
eformed“resonance-like”statesWe use almost thesame→parameterset as in the previous ReCo.
ü メソン⽣成時のフォトン
メソンと同じ⼤きさのv
2Consider only the contribution from M*=600MeV and pions
ü Recombination時のエネルギー保存を保証

he decay of resonance-like states

RHIC

quarkgTransverse flow

vT=0.52
Hadronization temperature

antiquarkmeson

Th=175MeV
Resonance-likestate(P, M*)
Fugacity
ReCo model
Resonance
decay
gu,d =1,gubar,dbar=0.9• パイオン⽣成のみを考慮(QM’17の時点)of pion spectrum reasonably well
ü Temperature@Hadronization: Th=175MeV
ü p0のcentrality dependenceを再現 (pT<4GeV/c)

Can describe centrality dependence

2) PHOTONS AT MESON PRODUCTION

Photon’s pt distribution @ RHIC

• ReCombination model + photon emission (板倉さんの発表)
k = 0.2
Slope (from 2-5 GeV)
Resonance: 0.328
Meson: 0.340
Gamma :0.320

Slope (from 2-5 GeV)
Resonance: 0.328
Meson: 0.340
Gamma :0.320

factor k = 0.2 determined at central collision• pTOverall
spectra：データを再現
Rough estimate
ü Low pTでのGapはより重いメソンの寄与で説明可
Consistent withnumerical result340/320 ~ 1.06
Slope of 320MeV is consistent with data for pt from 2 to 4 GeV.

•ellipticflow@ RHIC2)Photon’sPHOTONS ATMESONPRODUCTION
1qAssumepartonv2(asourceofflow)v, p0 1.3GeV
2 ( pT ) emission (板倉さんの発表)
3ReCombination model + photon

1 ( pT / p0 )v2 has the same magnitude
same shape as v2 of pions.
• pTPhoton’sspectra：データを再現& vand2：データを再現
Small momentum difference consistent with scaling (TM/Tg=1.06).
ü Low pTでのGapはより重いメソンの寄与で説明可
Cf: violation of NCQ
ü ALICEの結果も再現
scaling appears→ 時空発展を考慮したより本格的な計算に期待
in high pt region

NEW DATA FROM EXPERIMENTS

preliminary

1/2π p d2N/dp dy [(Gev/c)-2]

PH ENIX

10Au+Au → γ + X, |y|<0.350-20%,

sNN = 62.4 GeV

Fit ∝ Exp[-p /T eff ]T

1

Teff = 0.210 ± 0.028 ± 0.037 GeV

preliminary

Au+Au → γ + X, |y|<0.3520-40%,sNN = 62.4 GeV

Fit ∝ Exp[-p /T eff ]T

1

Teff = 0.193 ± 0.030 ± 0.023 GeV

10-1

TT

10-1

PH ENIX

10T

T

1/2π p d2N/dp dy [(Gev/c)-2]• New data from PHENIX
ü 検出器による外部光⼦変換を利⽤した測定− Au+Au: 62.4(0-20,20-40,MB), 39(MB)GeVü 仮想光⼦による内部光⼦変換を利⽤した測定− Cu+Cu: 200(0-40,MB)GeV

10-262.4GeV
0-20%

10-310-400.5

110-262.4GeV
20-40%

10-310-4
1.522.5

3p [GeV/c]
T

00.5

11.5

22.5

3p [GeV/c]
T

NEW DATA FROM EXPERIMENTS

preliminary

1/2π p d2N/dp dy [(Gev/c)-2]

PH ENIX

10Au+Au → γ + X, |y|<0.350-86%,

sNN = 62.4 GeV

Fit ∝ Exp[-p /T eff ]T1Teff = 0.211 ± 0.024 ± 0.044 GeV

PH ENIX

10preliminary

0-86%,

sNN = 39 GeV
T

Teff = 0.177 ± 0.031 ± 0.068 GeV

10-1

T

T

10-1

Au+Au → γ + X, |y|<0.35

Fit ∝ Exp[-p /T eff ]1TT1/2π p d2N/dp dy [(Gev/c)-2]• New data from PHENIX
ü 検出器による外部光⼦変換を利⽤した測定− Au+Au: 62.4(0-20,20-40,MB), 39(MB)GeVü 仮想光⼦による内部光⼦変換を利⽤した測定− Cu+Cu: 200(0-40,MB)GeV

10-2

10-3

62.4GeV
MB

10-3
10-4
00.5

110-2

39GeVMB-4

101.5

22.5

3p [GeV/c]
T

10-5

00.5

11.522.5

3p [GeV/c]
TNEW DATA FROM EXPERIMENTS• New data from PHENIX
ü 検出器による外部光⼦変換を利⽤した測定− Au+Au: 62.4(0-20,20-40,MB), 39(MB)GeVü 仮想光⼦による内部光⼦変換を利⽤した測定− Cu+Cu: 200(0-40,MB)GeV (広島⼤星野くんの結果)
1

1Cu+Cu → γ + X, |y|<0.35
sNN = 200 GeV, 0 - 40%
Direct photons
Aexp(-p T / T eff ) + power-law fit
T AA-scaled pp fit
T eff = 332±61(stat)±52(syst) MeV

10-2

10-5

10-3

Cu+Cu
0-40%

10-4

10-5PH ENIX

1Cu+CuMBPH ENIX

preliminary

10-60T eff = 288±49(stat)±50(syst) MeV

10-210-310-4Direct photons
Aexp(-p T / T eff ) + power-law fit
T AA-scaled pp fit

10-1d2N [(GeV/c)-2]12πp T dp T dy

10-1d2N [(GeV/c)-2]12πp T dp T dy

Cu+Cu → γ + X, |y|<0.35
sNN = 200 GeV, 0 - 94%

preliminary

23p T [GeV/c]

4510-60123p T [GeV/c]

45dN/dy : NPART DEPENDENCE• 超過収量に明らかなNpart依存性
ü A x Nparta Fit: a=1.35
ü 2体のパートン散乱による放射を仮定した(単純な)計算と無⽭盾：𝑅" ∝ 𝑁%& ⁄2 ⁄𝑉 * 𝑇 ※Npart~2-3Nqp
102

PH ENIX

preliminary

Au+Au → γ + X, |y| < 0.35
γ dir - γ prompt at sNN = 200 GeV PRC 91, 064904
γ dir at sNN = 62.4 GeV
γ dir at sNN = 39 GeV

dN/dy

10

1Cu+Cu → γ + X, |y| < 0.35
γ dir - γ prompt at sNN = 200 GeV

10-1pT > 1.0 GeV
Fit = A × Nαpart

10-2

α = 1.35 ± 0.09

10

Npart102TEFF :𝑺𝑵𝑵 DEPENDENCE

T (MeV/c)• Teff ≠ ⽣成物質の平均温度
ü Radial flowによるBlue-shift → Teff > T0350

PHENIX
39GeV0-86%300250PHENIX
200GeV
0-20%200PHENIX
62.4GeV0-20%

15010050ALICE
2.76TeV0-20%

10102103sNN (GeV)

b-CORRECTED TEFF :𝑺𝑵𝑵 DEPENDENCE

T (MeV/c)• Radial flow(𝛽)補正：𝑇011 = 𝑇3 1 + 𝛽⁄1 − 𝛽
ü 𝛽はp, K, pの測定結果にBlast-wave fitで算出したもの
350300●: b補正前◯: b補正後2502001501005010102103sNN (GeV)• T0~150MeV(~Tc) & 弱い 𝑠88 依存性→ Late stageからの寄与が⽀配的？初期温度への感度は？

今後期待される測定 (フォトン)• A+A dataü PHENIX: VTX導⼊後の外部変換光⼦測定。統計も10倍以上改善される⾒込み。
ü STAR: 内部変換光⼦測定結果(投稿済)ü ALICE: RUN-3での測定に期待(外部＆内部変換光⼦測定)
ü Low-pT photonが初期温度に敏感でない場合、thermal dielectron(1<mee<3GeV)測定がより重要 (PHENIX&ALICE)ü 光⼦偏極測定？(強磁場のピュアな信号)• Small system (p+p & p+A)
ü PHENIX: d+Au, He3+Auなどのmost-central eventsの解析が進⾏中
ü ALICE: p+p high-multiplicity events(東⼤村上さん)

レプトン対：低質量電⼦対QM前の理解：r MASS BROADENING
InIn@17.3 GeV: NA60, AIP Conf. Proc. 1322 (2010) 1

09/30/2015

Shuai Yang, Quark Matter 2015

• 低質量電⼦対について系統的な測定に成功
ü 広範囲のシステムサイズ＆衝突エネルギー− 17.3-200GeV (SPS&RHIC)
ü r mass broadeningで説明できる− ⽣成媒質のライフタイム依存性

HADES:Au+Au@√sNN=2.4GeV• Hot baryonic matter• Mee>150MeVに⼤きな超過収量

HADES:Au+Au@√sNN=2.4GeV• Hot baryonic matter• Mee>150MeVに⼤きな超過収量
ü r-baryon interaction + r
mass broadeningで説明できる (Coarse-grainedtransport model)

HADES:Au+Au@√sNN=2.4GeV• Hot baryonic matter• Mee>150MeVに⼤きな超過収量
ü r-baryon interaction + r
mass broadeningで説明できる (Coarse-grainedtransport model)
ü Exponential fit:
Tslope=71MeVBULK VISCOSITY EFFECT ON DI-LEPTONS• Bulk viscosityを計算に⼊れたモデル
ü IP-Glasma + Viscous Hydro + UrQMD [PRL115,132301]
ü ハドロンの実験結果(dN/dy, 𝑝: , vn)を記述
ü Hadronic matter(HM)からのdi-leptonを新たに導⼊Charged hadron v2<pT> for p, K, p

BULK VISCOSITY EFFECT ON DI-LEPTONS• Bulk viscosityを計算に⼊れたモデル
ü IP-Glasma + Viscous Hydro + UrQMD [PRL115,132301]
ü Bulk viscosityを考慮すると、HMでの温度降下が緩やかに

BULK VISCOSITY EFFECT ON DI-LEPTONS• Bulk viscosityを計算に⼊れたモデル
ü IP-Glasma + Viscous Hydro + UrQMD [PRL115,132301]
ü Bulk viscosityを考慮すると、HMでの温度降下が緩やかに→ HMからのdi-lepton収量＆v2が増加
dN/dyv2

HM
QGPQGP+HMQGP

今後期待される測定 (レプトン対)• 𝜌 mass broadeningのより系統的な測定
ü STAR BES-II & ALICE RUN-3− √sNN, pT依存性
ü Di-muon測定も (ALICE: 広島⼤志垣さん)

まとめ• 新しいデータ、モデル計算が出てきた。今後も活発な議論が期待出来る。(特にフォトン)ü Photons at Glasma & meson production
ü √sNN, Npartに対する系統的な測定→ Thermal di-lepton (IMR)がQGP初期温度決定の決め⼿になると思っている。
• 実験、理論ともに⽇本グループの活躍が⽬⽴っている。
ü 今後もより頻繁に議論する機会を持てると良い。