這篇論文包含了在7 TeV 和2.76 TeV 質子對撞下，光子散射截面積的測量。我
們使用了CMS 在7 TeV 和2.76 TeV 取得的35.9/pb 、232.1 /nb 的數據來做測
量。這兩個測量的結果也分別被使用來與7 TeV 和2.76 TeV 下，第二階量子色動
力學計算做比較，在這個比較裡，我們觀測到了理論計算與實驗一致的結果。 除
了和第二階量子色動力學計算做比較之外，論文裡也提供了2.76 TeV 下，鉛離子
對撞產生的光子散射截面積的測量。這個測量可以幫助我們獲得在經過計算加權
之後的鉛離子對撞產生的光子散射截面積與質子對撞產生的光子散射截面積的
比，有助於獲得質子對撞與鉛離子對撞初始狀態的資訊。另外關於測量方法方面，
在這兩個測量當中，我們都使用了量能器裡的單獨的能量累積程度來作為分辨信
號光子和背景粒子的係數，進而達到去除背景的目的。

Two measurements of the inclusive cross section for isolated prompt photon production in proton-proton
collisions at center-of-mass energy of 7 TeV and 2.76 TeV are present. For proton-proton collisions at
center-of-mass energy of 7 TeV/2.76 TeV, 35.9/pb / 232.1/nb of data recorded by CMS detector is used.
We first present the comparison between the next-to-leading-order perturbative QCD calculations and
measurements which we see consistency results between theory and data. Second, in order to get the ratio
of PbPb to pp isolated photon ET-di fferential yields scaled by the number of incoherent nucleon-nucleon
collisions, the result of inclusive cross section measurement for isolated prompt photon production in
2.76 TeV PbPb collisions is also shown. For both measurements at 7 TeV and at 2.76 TeV, photon
candidates are identi fied based on isolated energy deposits in the electromagnetic calorimeter.

[1] Electromagnetic calorimeter commissioning and performance with 7 tev data. CMS Note, EGM-10-002, 2010.
[2] Isolated photon reconstruction and identi cation at sqrts=7 tev. CMS Note, EGM-10-006, 2010.
[3] Measurement of the di erential isolated prompt photon production cross section in pp collisions at
sqrt(s) =7 tev. Phys.Rev., QCD-10-037, 2010.
[4] Photon reconstruction and identi cation at sqrt(s) = 7 tev. CMS Note, 2010.
[5] Electromagnetic physics objects commissioning with rst LHC data. CMS Note, 2010.
[6] G. Aad et al. Measurement of the inclusive isolated prompt photon cross section in pp collisions at
ps = 7 TeV with the ATLAS detector. Phys. Rev. D, 83:052005, 2011.
[7] Patrick Aurenche, Michel Fontannaz, Jean-Philippe Guillet, Eric Pilon, and Monique Werlen. A
New critical study of photon production in hadronic collisions. Phys.Rev., D73:094007, 2006.
[8] L. Bourhis, M. Fontannaz, and J.P. Guillet. Quarks and gluon fragmentation functions into photons.
Eur.Phys.J., C2:529{537, 1998.
[9] S. Catani, M. Fontannaz, J.P. Guillet, and E. Pilon. Cross-section of isolated prompt photons in
hadron hadron collisions. JHEP, 0205:028, 2002.
[10] Serguei Chatrchyan et al. Measurement of the Di erential Cross Section for Isolated Prompt Photon
Production in pp Collisions at 7 TeV. Phys.Rev., D84:052011, 2011.
[11] Serguei Chatrchyan et al. Observation and studies of jet quenching in PbPb collisions at nucleon-
nucleon center-of-mass energy = 2.76 TeV. Phys.Rev., C84:024906, 2011.
[12] Serguei Chatrchyan et al. Measurement of isolated photon production in pp and PbPb collisions at
sqrt(sNN) = 2.76 TeV. Phys.Lett., B710:256{277, 2012.
[13] K.J. Eskola, H. Paukkunen, and C.A. Salgado. EPS09: A New Generation of NLO and LO Nuclear
Parton Distribution Functions. JHEP, 0904:065, 2009.
[14] Hung-Liang Lai, Marco Guzzi, Joey Huston, Zhao Li, Pavel M. Nadolsky, et al. New parton
distributions for collider physics. Phys.Rev., D82:074024, 2010.
[15] Michael L. Miller, Klaus Reygers, Stephen J. Sanders, and Peter Steinberg. Glauber modeling in
high energy nuclear collisions. Ann.Rev.Nucl.Part.Sci., 57:205{243, 2007.
[16] K. Nakamura et al. Review of particle physics. J.Phys.G, G37:075021, 2010.