Brookhaven National Laboratory 3272015 T Sakaguchi Heavy Ion
高エネルギー重イオン衝突にお ける単光子の測定 坂口貴男 Brookhaven National Laboratory 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 1
単光子の様々な発生源 parton-medium interaction hard scatt Jet in-medium bremsstrahlung jet Brems. Jet-photon conversion jet-thermal s. QGP Rate hadron gas hadron decays Hadron Gas s. QGP Jet-Thermal 3/27/2015 1 10 Jet Brems. Hard Scatt T. Sakaguchi, Heavy Ion Tutorial@RIKEN Eg 107 log t (fm/c) 5
理論計算の一つ van Hees, Gale, Rapp, PRC 84, 054906 (2011) 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 6
単光子の測定方法 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 8
光子測定の測定器(PHENIXを例に) • 光子の測定には、主に、電磁カロリメータを使います。 5. 5 + 5. 5 cm – よい教科書: C. W. Fabjan and F. Gianotti, Rev. Mod. Phys. 75, 1243(2003) View From Beam 37. 5 c m Lead Scintillator Type 5 m 24768 Channels (Pb. Sc Type) Lead Glass Type (Pb. Gl Type) Fine Segment ( ≈ ≈0. 01/mod) 3/27/2015 Can separate two photons from π0 up to 25 Ge. V/c T. Sakaguchi, Heavy Ion Tutorial@RIKEN 12
実験結果の歴史 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 16
CERES Results on photons (No signal) • S+Au 200 Ge. V/n • s. NN=20 Ge. V • No excess photons over hadron decay photons Z. Phys. C 71(1996)571 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 3/27/2015 17
WA 80 results • S+Au at 200 Ge. V/u: s. NN=20 Ge. V – Onset for p. T>2. 5 Ge. V/c? T. Sakaguchi, Heavy Ion Tutorial@RIKEN WA 80, PRL 76, 3506(1996) 3/27/2015 18
WA 98 results • Third generation experiment, WA 98, showed the first significant result – Pb+Pb s. NN=17. 3 Ge. V, PRL 85, 3595(2000). p+Pb data shows initial nuclear effect Baumann, QM 2008 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 3/27/2015 19
RHIC金・金衝突における単光子 Au+Au: Phys. Rev. Lett. 109, 152302 (2012) RAA は 1と無矛盾: • • up to p. T~20 Ge. V/c 他の中心度でも同じ LHCでは、Z, Wでも同じものが見えています。 A theory: F. Arleo (JHEP 0609 (2006) 015)? • Isospin effect, in addition to jetquenching(BDMPS) and shadowing. 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 21
QGPからの単光子測定を目指して 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 23
新たな自由度を加えてみる • 実光子生成プロセスに対し、一定の確率で、内部転換による仮想光子が生成される • 仮想光子の質量が大きい領域(仮想度の高い領域)に注目する – p 0(135 Me. V/c 2)よりも、大きい質量領域 p. T (Ge. V/c) Compton q hard scatt g Cartoon only: sources of , mean p. T vs time e+ e- * q g* e+e- s. QGP hadron gas hadron decays virtuality Mass (Ge. V/c 2) 3/27/2015 1 2 1 10 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 107 log t (fm/c) 25
低横運動量の光子測定に成功 PHENIX, PRL. 104, 132301 (2010) ~21 % relative systematic error (on *direct/ *inclusive Ratio) ~20 % from measured h/p 0 ratio ~5 % acceptance 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 27
低横運動量の光子測定に成功 Fit results Cent. d. N/dy(p. T>1 Ge. V/c) T(Me. V) 2/DOF 0 -20% 1. 50 0. 23 0. 35 221 19 19 4. 7/4 20 -40% 0. 65 0. 08 0. 15 217 18 16 5. 0/3 MB 0. 49 0. 05 0. 11 233 14 19 3. 2/4 3/27/2015 PHENIX, PRL. 104, 132301 (2010) T. Sakaguchi, Heavy Ion Tutorial@RIKEN 28
光子の外部変換によるスペクトラ ar. Xiv: 1405. 3940 Min. Bias Au+Au 3/27/2015 Ncoll-scaled pp fit external conversion pp virtual photon pp in EMCal(Run 2003 data) pp in EMCal(Run 2006 data) Au. Au in EMCal(Run 2004 data) Au. Au from virtual photon(Run 4 data) T. Sakaguchi, Heavy Ion Tutorial@RIKEN 32
いくつかの理論との比較 ar. Xiv: 1405. 3940 仮定している衝突初期温度は、 300 -600 Me. V Linnyk et al. : PHSD transport model; Linnyk, Cassing, Bratkovskaya, P. R. C 89, 034908(2014) v. Hees et al. : Fireball model; van Hees, Gale, Rapp; P. R. C 84, 054906(2011) Shen et al. : Ohio hydro for two different initial conditions; Shen, Heinz, Paquet, Gale; P. R. C 84, 064903(2014) いずれのモデルも、レートを記述しきれ ていない 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 35
単光子生成レートのある考察 • クオーク・二体衝突の描像は実験結果と無矛盾 Cf. Nqpa: a= 1. 31+/- 0. 07 (stat) +/- 0. 03 (syst) Nparta: a= 1. 48+/- 0. 08 (stat) +/- 0. 04 (syst) 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN Calculation performed by A. Drees 38
単光子のフロー T. Sakaguchi, Heavy Ion Tutorial@RIKEN 3/27/2015 39
生成プロセスによる光子フローの予測 Photon sources v 2 v 3 Hadron-gas interaction Positive and sizable (following hadrons) QGP Positive and very small Primordial (jets) ~zerow Jet-induced Either positive or negative ? Magnetic field effect Positive, always above zero even at p. T=0 Zero s. NN=200 Ge. Vの金・金衝突において、QGPからの熱光子は、 v 2~0. 04 (20 -40% central), v 3 ~= v 2/(2 -3)と予測される 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 40
低横運動量単光子のv 2 と v 3 Syst. error source Value p 0 counting 15 -30% • 大きなフローが見えている • 中心度依存性は、v 2がより強く、v 3は弱い Photon ID 2 -3% Event plane ~22% v 3 ~ v 2/2 Rg - 1 ~50% Total ~30 -50% – ハドロンのフローに傾向が似ている • 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 43
Some results from the “other players” (STAR, ALICE) 3/27/2015 50 T. Sakaguchi, Heavy Ion Tutorial@RIKEN
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Virtual photons – STAR vs PHENIX STAR, Bingchu Huang, TPD 2014 PHENIX, PPG 086 Virtual photons, a la PHENIX, MB 3/27/2015 52 There appears to be a “tension” between the results T. Sakaguchi, Heavy Ion Tutorial@RIKEN
External conversion photons – ALICE vs PHENIX PPG 162 ALICE lower, but no real “tension” above 1 Ge. V/c – but the 0. 75 Ge. V/c is a bit worrysome. Also note the large difference between ALICE and PHENIX systematic errors. 3/27/2015 53 T. Sakaguchi, Heavy Ion Tutorial@RIKEN
Slides from ALICE (F. Bock, TPD 2014) 3/27/2015 54 T. Sakaguchi, Heavy Ion Tutorial@RIKEN
Slides from ALICE (F. Bock, TPD 2014) 3/27/2015 55 T. Sakaguchi, Heavy Ion Tutorial@RIKEN
The End 3/27/2015 T. Sakaguchi, Heavy Ion Tutorial@RIKEN 56
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