PHENIX Detector Overview

K. Adcox,45 S. S. Adler,4 M. Aizama,44 N. N. Ajitanand,31

Y. Akiba,16 H. Akikawa,19 J. Alexander,31 A. Al-Jamel,30

M. Allen,41 G. Alley,33 R. Amirikas,11 L. Aphecetche,39

Y. Arai,16 J. B. Archuleta,22 J. R. Archuleta,22 R. Armendariz,30

V. Armijo,22 S. H. Aronson,4 D. Autrey,21 R. Averbeck,32

T. C. Awes,33 B. Azmoun,32 A. Baldisseri,54 J. Banning,33

K. N. Barish,6 A. B. Barker,1 P. D. Barnes,22 J. Barrette,24

F. Barta,4 B. Bassalleck,29 S. Bathe,26 S. Batsouli,9

V. V. Baublis,34 A. Bazilevsky,14,37 R. Begay,32 J. Behrendt,29

S. Belikov,10,15 R. Belkin,4 F. G. Bellaiche,33 S. T. Belyaev,18

M. J. Bennett,22 Y. Berdnikov,40 S. Bhaganatula,15 J. C. Biggs,4

A. W. Bland,1 C. Blume,26 M. Bobrek,33 J. G. Boissevain,22

S. Boose,4 H. Borel,54 D. Borland,45 E. Bosze,6 S. Botelho,38

J. Bowers,21 C. Britton,33 L. Britton,33 M. L. Brooks,22

A. W. Brown,1 D. S. Brown,30 N. Bruner,29 W. L. Bryan,33

D. Bucher,26 H. Buesching,26 V. Bumazhnov,14 G. Bunce,4,37

J. Burward-Hoy,32 S. A. Butsyk,32,34 M. M. Cafferty,22

T. A. Carey,22 J. S. Chai,50 P. Chand,3 J. Chang,6

W. C. Chang,2 R. B. Chappell,11 L. L. Chavez,29

S. Chernichenko,14 C. Y. Chi,9 J. Chiba,16 M. Chiu,9

S. Chollet,52 R. K. Choudhury,3 T. Christ,32 T. Chujo,4,44

M. S. Chung,17,22 P. Chung,31 V. Cianciolo,33 D. J. Clark,22

Y. Cobigo,54 B. A. Cole,9 P. Constantin,15 R. Conway,22

K. C. Cook,15 D. W. Crook,11 H. Cunitz,9 R. Cunningham,22

M. Cutshaw,33 D. G. D’Enterria,39 C. M. Dabrowski,4

G. Danby,4 S. Daniels,33 A. Danmura,44 G. David,4

A. Debraine,52 H. Delagrange,39 J. DeMoss,29 A. Denisov,14

A. Deshpande,37 E. J. Desmond,4 O. Dietzsch,38 B. V. Dinesh,3

J. L. Drachenberg,1 O. Drapier,52 A. Drees,32 R. du Rietz,23

A. Durum,14 D. Dutta,3 K. Ebisu,28 M. A. Echave,22

Y. V. Efremenko,33 K. El Chenawi,45 M. S. Emery,33 D. Engo,4

A. Enokizono,13 K. Enosawa,44 H. En’yo,19,36 N. Ericson,33

S. Esumi,44 V. A. Evseev,34 L. Ewell,4 O. Fackler,21

J. Fellenstein,45 T. Ferdousi,6 J. Ferrierra,32 D. E. Fields,29

F. Fleuret,52 S. L. Fokin,18 B. Fox,37 Z. Fraenkel,47 S. Frank,33

A. Franz,4 J. E. Frantz,9 A. D. Frawley,11 J. Fried,4

J. P. Freidberg,25 E. Fujisawa,42 H. Funahashi,19 S. -Y. Fung,6

S. Gadrat,53 J. Gannon,4 S. Garpman,23 F. Gastaldi,52

T. F. Gee,33 R. Gentry,33 T. K. Ghosh,45 P. Giannotti,4

A. Glenn,41 A. L. Godoi,38 M. Gonin,52 G. Gogiberidze,41

J. Gosset,54 Y. Goto,37 R. Granier de Cassagnac,52

S. V. Greene,45 V. Griffin,11 M. Grosse Perdekamp,37

S. K. Gupta,3 W. Guryn,4 H. -A. Gustafsson,23 T. Hachiya,13

J. S. Haggerty,4 S. Hahn,22 J. Halliwell,33 H. Hamagaki,8

R. H. Hance,1 A. G. Hansen,22 H. Hara,28 J. Harder,4

G. W. Hart,22 E. P. Hartouni,21 A. Harvey,21 L. Hawkins,4

R. S. Hayano,43 H. Hayashi,44 N. Hayashi,36 X. He,12 N. Heine,26

F. Heistermann,4 S. Held,41 T. K. Hemmick,32 J. M. Heuser,32

M. Hibino,46 J. S. Hicks,33 R. Higuchi,44 J. C. Hill,15

T. Hirano,44 D. S. Ho,48 R. Hoade,4 W. Holzmann,31

K. Homma,13 B. Hong,17 A. Hoover,30 C. T. Hunter,1

D. E. Hurst,33 R. Hutter,32 T. Ichihara,36,37 V. V. Ikonnikov,18

K. Imai,19,36 M. Inaba,44 M. S. Ippolitov,18 L. Davis Isenhower,1

L. Donald Isenhower,1 M. Ishihara,36,37 M. Issah,31

V. I. Ivanov,34 B. V. Jacak,32,37 G. Jackson,33 J. Jackson,4

D. Jaffe,33 U. Jagadish,33 W. Y. Jang,17 R. Jayakumar,25

J. Jia,32 B. M. Johnson,4 J. Johnson,33 S. C. Johnson,21,32

J. P. Jones,33 K. Jones,4 K. S. Joo,27 D. Jouan,51 S. Kahn,4

F. Kajihara,8 S. Kametani,46 Y. Kamyshkov,33,41

A. Kandasamy,4 J. H. Kang,48 M. R. Kann,34 S. S. Kapoor,3

J. Kapustinsky,22 K. V. Karadjev,18 V. Kashikhin,10 S. Kato,44

K. Katou,46 H. -J. Kehayias,4 M. A. Kelley,4 S. Kelly,9

M. Kennedy,11 B. Khachaturov,47 A. V. Khanzadeev,34

A. Khomutnikov,40 J. Kikuchi,46 D. J. Kim,48 D. -W. Kim,49

G. -B. Kim,52 H. J. Kim,48 S. Y. Kim,48 Y. G. Kim,48

W. W. Kinnison,22 E. Kistenev,4 A. Kiyomichi,44

C. Klein-Boesing,26 S. Klinksiek,29 L. Kluberg,52

2

H. Kobayashi,37 V. Kochetkov,14 D. Koehler,29 T. Kohama,13

B. G. Komkov,34 M. L. Kopytine,32 K. Koseki,44

L. Kotchenda,34,35 D. Kotchetkov,6 Iou. A. Koutcheryaev,18

A. Kozlov,47 V. S. Kozlov,34 P. A. Kravtsov,34 P. J. Kroon,4

C. H. Kuberg,1 L. G. Kudin,34 M. Kurata-Nishimura,44

V. V. Kuriatkov,34 K. Kurita,36,37 Y. Kuroki,44 M. J. Kweon,17

Y. Kwon,48 G. S. Kyle,30 J. J. LaBounty,4 R. Lacey,31

J. G. Lajoie,15 J. Lauret,31 A. Lebedev,15 V. A. Lebedev,18

V. D. Lebedev,34 D. M. Lee,22 S. Lee,49 M. J. Leitch,22 M. Lenz,4

W. Lenz,4 X. H. Li,6 Z. Li,7,36 B. Libby,15 M. Libkind,21

W. Liccardi,4 D. J. Lim,48 S. Lin,4 M. X. Liu,22 X. Liu,7

Y. Liu,51 Z. Liu,7 E. Lockner,29 N. Longbotham,1 J. D. Lopez,22

R. Machnowski,4 C. F. Maguire,45 J. Mahon,4 Y. I. Makdisi,4

V. I. Manko,18 Y. Mao,7,36 S. Marino,4 S. K. Mark,24

S. Markacs,9 D. G. Markushin,34 G. Martinez,39

X. B. Martinez,22 M. D. Marx,32 A. Masaike,19 F. Matathias,32

T. Matsumoto,8,46 P. L. McGaughey,22 M. C. McCain,1

J. Mead,4 E. Melnikov,14 Y. Melnikov,14 W. Z. Meng,4

M. Merschmeyer,26 F. Messer,32 M. Messer,4 Y. Miake,44

N. M. Miftakhov,34 S. Migluolio,25 J. Milan,31 T. E. Miller,45

A. Milov,47 K. Minuzzo,21 S. Mioduszewski,4,41 R. E. Mischke,22

G. C. Mishra,12 J. T. Mitchell,4 Y. Miyamoto,44 A. K. Mohanty,3

B. C. Montoya,22 A. Moore,33 T. Moore,33 D. P. Morrison,4

G. G. Moscone,33 J. M. Moss,22 F. Muhlbacher,32

M. Muniruzzaman,6 J. Murata,36 M. M. Murray,22

M. Musrock,33 S. Nagamiya,16 Y. Nagasaka,28 J. L. Nagle,9

Y. Nakada,19 T. Nakamura,13 B. K. Nandi,6 J. Negrin,4

J. Newby,41 L. Nikkinen,24 S. A. Nikolaev,18 P. Nilsson,23

S. Nishimura,8 A. S. Nyanin,18 J. Nystrand,23 E. O’Brien,4

P. O’Conner,4 F. Obenshain,33 C. A. Ogilvie,15 H. Ohnishi,4,13

I. D. Ojha,5,45 M. Ono,44 V. Onuchin,14 A. Oskarsson,23

L. Osterman,23 I. Otterlund,23 K. Oyama,8,43 L. Paffrath,4,∗

A. P. T. Palounek,22 C. E. Pancake,32 V. S. Pantuev,32

V. Papavassiliou,30 S. F. Pate,30 T. Peitzmann,26 R. Petersen,21

A. N. Petridis,15 C. H. Pinkenburg,4,31 R. P. Pisani,4

3

P. Pitukhin,14 T. Plagge,15 F. Plasil,33 M. Pollack,32,41

K. Pope,41 R. Prigl,4 M. L. Purschke,4 A. K. Purwar,32

J. M. Qualls,1 S. Rankowitz,4 G. Rao,33 R. Rao,33 M. Rau,4

I. Ravinovich,47 R. Raynis,4 K. F. Read,33,41 K. Reygers,26

G. Riabov,34 V. G. Riabov,34,40 Yu. G. Riabov,34

S. H. Robinson,22 G. Roche,53 A. Romana,52 M. Rosati,15

E. V. Roschin,34 A. A. Rose,45 P. Rosnet,53 R. Roth,22

R. Ruggiero,4 S. S. Ryu,48 N. Saito,36,37 A. Sakaguchi,13

T. Sakaguchi,8,46 S. Sakai,44 H. Sako,44 T. Sakuma,36,42

S. Salomone,32 V. M. Samsonov,34 W. F. Sandhoff, Jr.,4

L. Sanfratello,29 T. C. Sangster,21 R. Santo,26 H. D. Sato,19,36

S. Sato,44 R. Savino,4 S. Sawada,16 B. R. Schlei,22

R. Schleuter,20 Y. Schutz,39 M. Sekimoto,16 V. Semenov,14

R. Seto,6 Y. Severgin,10 A. Shajii,25 V. Shangin,10 M. R. Shaw,1

T. K. Shea,4 I. Shein,14 V. Shelikhov,14 T. -A. Shibata,36,42

K. Shigaki,16 T. Shiina,22 T. Shimada,44 Y. H. Shin,48

I. G. Sibiriak,18 D. Silvermyr,23 K. S. Sim,17 J. Simon-Gillo,22

M. Simpson,33 C. P. Singh,5 V. Singh,5 W. Sippach,9

M. Sivertz,4 H. D. Skank,15 S. Skutnik,15 G. A. Sleege,15

D. C. Smith,33 G. D. Smith,22 M. Smith,33 A. Soldatov,14

G. P. Solodov,34 R. A. Soltz,21 W. E. Sondheim,22

S. Sorensen,33,41 I. Sourikova,4 F. Staley,54 P. W. Stankus,33

N. Starinsky,24 S. Steffens,41 E. M. Stein,4 P. Steinberg,9

E. Stenlund,23 M. Stepanov,30 A. Ster,55 J. Stewering,26

W. Stokes,4 S. P. Stoll,4 M. Sugioka,36,42 T. Sugitate,13

J. P. Sullivan,22 Y. Sumi,13 Z. Sun,7 M. Suzuki-Nara,44

E. M. Takagui,38 A. Taketani,36 M. Tamai,46 K. H. Tanaka,16

Y. Tanaka,28 E. Taniguchi,36,42 M. J. Tannenbaum,4

V. I. Tarakanov,34 O. P. Tarasenkova,34 J. D. Tepe,1 R. Thern,4

J. H. Thomas,21 J. L. Thomas,32 T. L. Thomas,29

W. D. Thomas,15 G. W. Thornton,22 W. Tian,7,41 R. Todd,33

J. Tojo,19,36 F. Toldo,4 H. Torii,19,36 R. S. Towell,1,22

J. Tradeski,4 V. A. Trofimov,34 I. Tserruya,47 H. Tsuruoka,44

A. A. Tsvetkov,18 S. K. Tuli,5 G. Turner,33 H. Tydesjo,23

N. Tyurin,14 S. Urasawa,44 A. Usachev,14 T. Ushiroda,28

4

H. W. van Hecke,22 M. Van Lith,4 A. A. Vasiliev,18 V. Vasiliev,10

M. Vassent,53 C. Velissaris,30 J. Velkovska,32 M. Velkovsky,32

W. Verhoeven,26 L. Villatte,41 A. A. Vinogradov,18

V. I. Vishnevskii,34 M. A. Volkov,18 W. Von Achen,4

A. A. Vorobyov,34 E. A. Vznuzdaev,34 M. Vznuzdaev,34

J. W. Walker,33 Y. Wan,7 H. Q. Wang,6 S. Wang,11

Y. Watanabe,36,37 L. C. Watkins,33 T. Weimer,15 S. N. White,4

B. R. Whitus,33 C. Williams,33 P. S. Willis,1 A. L. Wintenberg,33

C. Witzig,4 F. K. Wohn,15 K. Wolniewicz,4

B. G. Wong-Swanson,22 L. Wood,15 C. L. Woody,4

L. W. Wright,11 J. Wu,32 W. Xie,6,47 N. Xu,41 K. Yagi,44

R. Yamamoto,21 Y. Yang,4,7 S. Yokkaichi,36 Y. Yokota,44

S. Yoneyama,42 G. R. Young,33 I. E. Yushmanov,18 W. A. Zajc,9

C. Zhang,9 L. Zhang,9 Z. Zhang,32 S. Zhou7

(The PHENIX Collaboration)

1Abilene Christian University, Abilene, TX 79699, USA2Institute of Physics, Academia Sinica, Taipei 11529, Taiwan

3Bhabha Atomic Research Centre, Bombay 400 085, India4Brookhaven National Laboratory, Upton, NY 11973-5000, USA

5Department of Physics, Banaras Hindu University, Varanasi 221005, India6University of California - Riverside, Riverside, CA 92521, USA

7China Institute of Atomic Energy (CIAE), Beijing, People’s Republic of China8Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1

Hongo, Bunkyo, Tokyo 113-0033, Japan9Columbia University, New York, NY 10027 and Nevis Laboratories, Irvington,

NY 10533, USA10Efremov Institute for Electrophysical Research, St. Petersburg, Russia

11Florida State University, Tallahassee, FL 32306, USA12Georgia State University, Atlanta, GA 30303, USA

13Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan14Institute for High Energy Physics (IHEP), Protvino, Russia

15Iowa State University, Ames, IA 50011, USA16KEK, High Energy Accelerator Research Organization, Tsukuba-shi, Ibaraki-ken

305-0801, Japan17Korea University, Seoul, 136-701, Korea

18Russian Research Center ”Kurchatov Institute”, Moscow, Russia19Kyoto University, Kyoto 606, Japan

20Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA21Lawrence Livermore National Laboratory, Livermore, CA 94550, USA

22Los Alamos National Laboratory, Los Alamos, NM 87545, USA23Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden

5

24McGill University, Montreal, Quebec H3A 2T8, Canada25Plasma Science and Fusion, Center Massachusetts Institute of Technology,

Cambridge, MA 02139, USA26Institut fur Kernphysik, University of Munster, D-48149 Munster, Germany

27Myongji University, Yongin, Kyonggido 449-728, Korea28Nagasaki Institute of Applied Science, Nagasaki-shi, Nagasaki 851-0193, Japan

29University of New Mexico, Albuquerque, NM 87131, USA30New Mexico State University, Las Cruces, NM 88003, USA

31Chemistry Department, State University of New York - Stony Brook, StonyBrook, NY 11794, USA

32Department of Physics and Astronomy, State University of New York - StonyBrook, Stony Brook, NY 11794, USA

33Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA34PNPI, Petersburg Nuclear Physics Institute, Gatchina, Russia

35State Interphysica, Protvino, Russia36RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama

351-0198, Japan37RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, NY

11973-5000, USA38Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo

CEP05315-970, Brazil39SUBATECH (Ecole des Mines de Nantes, IN2P3/CNRS, Universite de Nantes)

BP 20722 - 44307, Nantes-cedex 3, France40St. Petersburg State Technical University, St. Petersburg, Russia

41University of Tennessee, Knoxville, TN 37996, USA42Department of Physics, Tokyo Institute of Technology, Tokyo, 152-8551, Japan

43University of Tokyo, Tokyo, Japan44Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, Japan

45Vanderbilt University, Nashville, TN 37235, USA46Waseda University, Advanced Research Institute for Science and Engineering, 17

Kikui-cho, Shinjuku-ku, Tokyo 162-0044, Japan47Weizmann Institute, Rehovot 76100, Israel

48Yonsei University, IPAP, Seoul 120-749, Korea49Kangnung National University, Kangnung, 210-702, Korea

50C.A.L., Korea Cancer Hospital, Seoul, 139-706, Korea51I.P.N., BP 1, 91406 Orsay, France

52L.L.R., Ecole Polytechnique, 91128 Palaiseau, France53L.P.C., Universite Blaise Pascal, 63177 Aubiere Cedex, France

54DSM/Dapnia/SPhN, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France55Individual Participant: KFKI Research Institute for Particle and Nuclear

Physics (RMKI), Budapest, Hungary

6

The PHENIX detector is designed to perform a broad study of A-A,p-A, and p-p collisions to investigate nuclear matter under extremeconditions. A wide variety of probes, sensitive to all timescales, areused to study systematic variations with species and energy as wellas to measure the spin structure of the nucleon. Designing for theneeds of the heavy-ion and polarized-proton programs has produceda detector with unparalleled capabilities. PHENIX measures elec-tron and muon pairs, photons, and hadrons with excellent energyand momentum resolution. The detector consists of a large num-ber of subsystems that are discussed in other papers in this volume.The overall design parameters of the detector are presented.

1 Introduction

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Labora-tory accelerates nuclear beams from protons to gold. For the heaviest beams anenergy of 100 GeV/nucleon is reached. Four detectors, BRAHMS, PHENIX,PHOBOS and STAR, are operating to study collisions ranging from p-p to Au-Au. The Pioneering High Energy Nuclear Interaction eXperiment (PHENIX)is carried out by a collaboration of about 500 physicists and engineers from54 participating institutions in 13 countries [1]. Fig.1 shows a subset of theCollaboration standing in front of parts of the PHENIX detector.

The PHENIX experiment probes several fundamental features of the stronginteraction. A prime goal for experiments with heavy ion beams is to producea deconfined state of nuclear matter called the Quark Gluon Plasma (QGP)and study it’s properties. This is thought to be the state of the universe aµs after its birth in the “big bang”. Measuring leptons and photons probesthe QGP phase directly, while studying the copiously produced hadrons givesinformation on the later hadronization of the QGP. RHIC also provides theopportunity to study collisions of polarized protons. The aim is to measurethe spin structure of the nucleon [2].

In order to carry out this broad physics agenda the PHENIX detector utilizesa variety of detector technologies. It uses global detectors to characterize thecollisions, a pair of central spectrometers at mid rapidity to measure electrons,hadrons, and photons, and a pair of forward spectrometers to measure muons.Each spectrometer has a large geometric acceptance of about one steradianand excellent energy and momentum resolution and particle identification.

7

Fig. 1. Members of the PHENIX collaboration in front of the PHENIX detector.

2 Physics Goals of PHENIX

Quantum Chromodynamics (QCD) predicts that heavy nuclei colliding at ul-trarelativistic energies will undergo a phase transition from hadronic matterto a deconfined state of quarks and gluons moving freely over a volume ap-proximately 10fm3, namely the QGP.

This process can be thought of as proceeding throught a series of steps from theinitial collision through QGP formation (deconfinement) and possible chiralsymmetry restoration. The QGP would thermalize followed by expansion andcooling leading to hadronization. PHENIX is able to probe each phase ofthe above process by virtue of its ability to study the rare processes involvingphotons, electrons and muons as well as the predominant hadronic production.The experiment has a high rate capability and fine granularity combined withexcellent momentum, energy and mass resolution.

Direct photons and lepton pairs which emerge from the collision with a mini-mum of final state interaction are sensitive to the full time evolution from theinitial state through thermalization. The capability to measure direct photonsover a wide range of pT is unique to PHENIX and is important for relatingtheir momentum to the temperature of the emitting source.

8

Jets from the hard scattering of constituent quarks and gluons are producedin the initial state and are sensitive to the properties of the medium duringthe evolution so that a significant modification of the structure of the jet isexpected if a QGP is formed. PHENIX studies the deconfined state and Debyescreening by observing the yields of the J/Ψ and Ψ′ relative to that of the Υ.Chiral symmetry restoration is predicted to result in the reduction of quarkmasses and possible changes in the lifetime and width of the φ and possiblythe ρ and ω. All of the above vector mesons are studied by observation of theirdecays into lepton pairs.

After hadronization the expansion of the fireball is studied by measurementof Hanbury-Brown-Twiss correlations and the coalescence probabilities of var-ious nuclei and anti-nuclei give insights into the space-time evolution of thecollision. Precision time of flight (ToF) allows measurement of the identifiedcharged hadron spectrum over a wide pT range. Many of the above signals canalso be produced from interactions between particles in hot hadronic matter.It is thus necessary to understand the purely hadronic effects. For this rea-son PHENIX studies the above signals using p-p and p-A collisions to gain abetter understanding of effects distorting signals from the QGP.

A second major goal of the PHENIX experiment is to measure the spin struc-ture of the nucleon. RHIC accelerates beams of polarized protons up to 250GeV with polarizations up to 50%. Work of the EMC [3] collaboration andothers indicated that the fraction of the proton spin carried by the quarks wasonly about half of the expected value. PHENIX studies the gluon polarizationby measuring high pT prompt photon production using the highly segmentedEM Calorimeter to minimize interference from photons from π0 decays. Theanti-quark polarization is measured by observing the parity violating asym-metry for W production. The W particles are identified by the detection ofmuons or electrons with pT ≥ 20GeV/c using the PHENIX north and southmuon arms or the central spectrometer, respectively.

3 PHENIX Detector Subsystems

The PHENIX detector comprises four instrumented spectrometers or arms andthree global detectors [4]. The detector consists of a number of subsystems.The rapidity and φ coverages and other features of these subsystems is givenin Table 1 and a perspective drawing of the PHENIX detector with the majorsubsystems labeled is shown in Fig.2. Also an overview of the subsystems isgiven below. The east and west central arms are centered at zero rapidity andinstrumented to detect electrons, photons and charged hadrons. The northand south forward arms have full azimuthal coverage and are instrumented todetect muons. Each of the four arms has a geometric acceptance of approxi-

9

Fig. 2. A cutaway drawing of the PHENIX detector. Labeled arrows point to themajor detector subsystems.

mately one steradian. The global detectors measure the start time, vertex andmultiplicity of the interactions. A photograph of the PHENIX detector fromabove is shown in Fig.3.

3.1 Global Detectors

In order to characterize the nature of an event following a heavy ion collision,three global detectors are employed. They consist of Zero-Degree Calorimeters(ZDC), Beam- Beam Counters (BBC) and the Multiplicity-Vertex Detector(MVD). A pair of ZDC’s [5] detect neutrons from grazing collisions and forma trigger for the most peripheral collisions. The ZDC is used by all four RHICdetectors and is discussed elsewhere in this volume [6]. A pair of BBCs [7]provide a measure of the time-of-flight of forward particles to determine thetime of a collision, provide a trigger for the more central collisions and providea measure of the collision position along the beam axis. The MVD [7] provides

10

Fig. 3. Photograph of the PHENIX detector viewed from north to south. The centralarms are visible on the right (west) and east (left) sides. In the back the south muonmagnet and the muon identifier detectors are visible

a more precise determination of event position and multiplicity and measuresfluctuations of the charged particle distributions. It is composed of concentricbarrels of silicon-strip detectors and endcaps made of silicon pads. Recently aNormalization Trigger Counter (NTC) [7] has been added between the MVDendcaps and the central magnet pole tips. The NTC extends the coverage ofthe BBC for p-p and p-A running.

3.2 Central Spectrometers

The magnetic field for the central spectrometer is supplied by the centralmagnet [8] that provides an axial field parallel to the beam and around theinteraction vertex. The central arms consist of tracking systems for chargedparticles and electromagnetic calorimetry. The calorimeter [9] is the outermostsubsystem on the central arms and provides measurements of both photonsand energetic electrons. A lead-scintillator (PbSc) calorimeter is used for goodtiming and a lead-glass (PbGl) calorimeter gives good energy resolution.

The tracking system uses three sets of Pad Chambers (PC) [10] to provideprecise three-dimensional space points needed for pattern recognization. The

11

Table 1Summary of the PHENIX Detector Subsystems.

Element ∆η ∆φ Purpose and Special Features

Magnet: central (CM) ±0.35 360◦ Up to 1.15 T·m.

muon (MMS) -1.1 to -2.2 360◦ 0.72 T·m for η = 2

muon (MMN) 1.1 to 2.4 360◦ 0.72 T·m for η = 2

Silicon (MVD) ±2.6 360◦ d2N/dηdφ, precise vertex,

reaction plane determination

Beam-beam (BBC) ±(3.1 to 3.9) 360◦ Start timing, fast vertex.

NTC ±(1 to 2) 320◦ Extend coverage of BBC for p-p and p-A.

ZDC ±2 mrad 360◦ Minimum bias trigger.

Drift chambers (DC) ±0.35 90◦×2 Good momentum and mass resolution,

∆m/m = 0.4% at m = 1GeV.

Pad chambers (PC) ±0.35 90◦×2 Pattern recognition, tracking

for nonbend direction.

TEC ±0.35 90◦ Pattern recognition, dE/dx.

RICH ±0.35 90◦×2 Electron identification.

ToF ±0.35 45◦ Good hadron identification, σ <100 ps.

T0 ±0.35 45◦ Improve ToF timing for p-p and p-A.

PbSc EMCal ±0.35 90◦+45◦ For both calorimeters, photon and electron

detection.

PbGl EMCal ±0.35 45◦ Good e±/π± separation at p > 1 GeV/c by

EM shower and p < 0.35 GeV/c by ToF.

K±/π± separation up to 1 GeV/c by ToF.

µ tracker: (µTS) -1.15 to -2.25 360◦ Tracking for muons.

(µTN) 1.15 to 2.44 360◦ Muon tracker north installed for year-3

µ identifier: (µIDS) -1.15 to -2.25 360◦ Steel absorbers and Iarocci tubes for

(µIDN) 1.15 to 2.44 360◦ muon/hadron separation.

precise projective tracking of the Drift Chambers (DC) [10] is the basis ofthe excellent momentum resolution. A Time Expansion Chamber (TEC) [10]in the east arm provides additional tracking and particle identification. TheTime-of-Flight (ToF) and Ring-Imaging CHerenkov (RICH) detectors alsoprovide particle identification [11]. The 85 ps timing resolution of the ToF al-

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lows separation of kaons from pions up to 2.5 GeV/c and proton identificationout to 5 Gev/c. For p-p running the ToF timing resolution would be poorerthan for heavy ions due to a reduced number of particles in the BBC. The ToFtiming is improved by the use of a T0 counter [11] outside the barrel of theMVD. This is needed for p-p and p-A experiments. The RICH provides sepa-ration of electrons from the large number of copiously produced pions. Usinginformation from the RICH, the TEC and the electromagnetic calorimeter itis possible to reject pion contamination of identified electrons to one part in104 over a wide range of momentum.

3.3 Muon Spectrometers

The two forward muon spectrometers [12] give PHENIX acceptance for J/Ψdecaying into dimuons at rapidities of −2.25 ≤ y ≤ −1.15 for the south armand 1.15 ≤ y ≤ 2.44 for the north arm. Each spectrometer is based on a muontracker inside a radial magnetic field [8] followed by a muon identifier, bothwith full azimuthal acceptance. The muon trackers consist of three stations ofmulti-plane drift chambers that provide precision tracking. The muon identi-fiers consist of alternating layers of steel absorbers and low resolution trackinglayers of streamer tubes of the Iarocci type. With this combination the pioncontamination of identified muons is typically 3 × 10−3. The complete northarm will be installed prior to the year-3 PHENIX run.

3.4 Electronics and Computing

PHENIX selects and archives events of potential physics interest at the max-imum rate consistent with the available RHIC luminosity. The channel countfor the PHENIX detector is large and details for the various subdetectors isgiven in Table2. Note that for some subsystems two ADCs are required perchannel to get the needed dynamic range. In order to obtain a high data-collection efficiency a high degree of coordination between the electronics andcomputing efforts is required. Custom Front-End Electronics (FEE) were de-signed for the PHENIX subsystems. Signals from the FEEs [13] are trans-ported by optical fibers to the level-1 trigger [13] that processes signals from anumber of subsystems and then either accepts or rejects the event. The triggeroperates in a synchronous pipelined mode with a latency of 40 beam cross-ings, and thus generates a decision for each crossing. The timing of the aboveoperations is coordinated by a master timing system [13] that distributes theRHIC clocks to granule timing modules that communicate with the FEEs.

In order to study the rare event physics for which PHENIX was designed, itis necessary to have a higher level of event rejection than possible with the

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Table 2Channel counts, digitizer channels and LVL-1 trigger bits/sums for PHENIX.

Subsystem Detector ADC TDC LVL-1

Symbol Channels Channels Channels Inputs

BB 128 128 256 128 bits

MVD 20,736 20,736

NTC 8 8 16 8 bits

DC 12,800 12,800

PC 172,800 172,800

TEC 20,480 20,480

RICH 5120 5120 5120 256 bits

TOF 1920 1920 1920 1920 bits

T0 22 22 44 22 bits

EMCal 24,768 49,536 24,768 688 bits

µTR 20,480 20,480

µID 3,660 3,660 3,660 hits

level-1 trigger alone. Therefore a level-2 software trigger [13] that makes itsselection after a complete event is assembled was developed.

Once the level-1 trigger accepts an event, the data from the various subsystemsis routed via fiber-optic cable to the data collection modules [13] that interactwith the subsystems by means of daughter cards that format and zero-suppressthe data. Data packets are generated by digital signal processors and sent toevent builders [13] that assemble the events in their final form. The controland monitoring of the electronics and triggering is handled by the On-LineComputing System (ONCS) [14]. ONCS configures and initializes the on-linesystem, monitors and controls the data flow and interlocks the data acquisitionprocess with the slow controls systems. After the data is collected the off-line system [14] provides event reconstruction, data analysis and informationmanagement. It provides the tools to convert raw data into physics results.

4 Conclusion

The performance of the PHENIX detector is summarized in Table 3. It isdesigned to carry out the broadest possible study of collisions from Au-Au top-p. The goal is to examine nuclear matter under a variety of extreme condi-

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Table 3Performance of the PHENIX Detector.

Physics Year-2 Version

Electrons π/e < 10−4 at p ≤ 4.7 GeV/c

RICH for < 4.7 GeV/c

TEC (dE/dx) for < 2 GeV/c

EMCal for > 0.5 GeV/c

Photons pT ≥ 1 GeV/c for 0.5 sr with PbGl.

pT ≥ 1 GeV/c for 1.5 sr with PbSc.

Single γs resolved from merging π0 → γ + γ

out to PT ≥ 25 GeV/c.

Hadrons ≤ 2.3 GeV/c π for 0.38 sr

≤ 1.6 GeV/c K for 0.38 sr

≤ 5.0 GeV/c p for 0.38 sr

TOF with σ < 100 ps.

Muons π/µ < 3 × 10−3 at p ≥ 2.3 GeV/c

with 5 layers of µID.

Global d2N/dηdφ for |η| < 2.6

tions using a variety of probes sensitive to all time scales. In addition, studiesof various signals are carried out as a function of both energy and nuclearspecies in order to separate QGP signals from those of hadronic origin. An-other goal is to measure the spin structure of the nucleon by determining thecontributions from anti-quarks and gluons. The above goals have resulted inthe production of a detector with unparalled capabilities. In the summer of2000 a number of Au-Au collisions were observed between Au ions with ener-gies of 65 GeV/nucleon using the central spectrometer. In the first PHENIXphysics publication [15] results from the measurement of the charged-particlemultiplicity are presented. Subsequently results from the first measurementof energy transverse to the beam direction [16], on mass dependence of two-pion correlations [17], on measurement of single electrons with implications forcharm production [18] and on the centrality dependence of pion, kaon, pro-ton and antiproton production [19] have been published and studies of resultsfrom Au-Au collisions with 100 Gev/nucleon beams are underway.

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5 Acknowledgements

We thank the staff of the RHIC project, Collider-Accelerator, and PhysicsDepartments at BNL and the staff of PHENIX participating institutions fortheir vital contributions. We acknowledge support from the Department ofEnergy and NSF (U.S.A.), Monbu-sho and STA (Japan), RAS, RMAE, andRMS (Russia), BMBF and DAAD (Germany), FRN, NFR, and the Wallen-berg Foundation (Sweden), MIST and NSERC (Canada), CNPq and FAPESP(Brazil), IN2P3/CNRS and DAPNIA/CEA (France), DAE (India), KRF andKOSEF (Korea) and the US-Israel Binational Science Foundation.

References

[1] Y. Akiba et al., Nucl. Phys. A638 (1998) 565c.

[2] N. Saito et al., Nucl. Phys. A638 (1998) 575c.

[3] J. Ashman et al., (EMCollab.) Phys. Lett. B 202 (1988) 603; J.J. Aubert et al..(EMCollab.) Phys. Lett. B 123 (1983) 275.

[4] PHENIX Conceptual Design Report, BNL 1993 (unpublished).

[5] C. Adler et al., Nucl. Instr. and Meth. A 470 (2001) 488.

[6] ZDC article this volume.

[7] Article entitled “PHENIX Inner Detectors” this volume.

[8] Article entitled “PHENIX Magnet System” this volume.

[9] Article entitled “PHENIX Calorimeter” this volume.

[10] Article entitled “PHENIX Central Arm Tracking Detectors” this volume.

[11] Article entitled “PHENIX Central Arm Particle I.D. Detectors” this volume.

[12] Article entitled “PHENIX Muon Arms” this volume.

[13] Article entitled “PHENIX On-Line Systems” this volume.

[14] Article entitled “PHENIX On-Line and Off-Line Computing” this volume.

[15] K. Adcox et al., Phys. Rev. Lett. 86 (2001) 3500.

[16] K. Adcox et al.. Phys. Rev. Lett. 87 (2001) 052301.

[17] K. Adcox et al.. Phys. Rev. Lett. 88 (2002) 192302.

[18] K. Adcox et al.. Phys. Rev. Lett. 88 (2002) 192303.

[19] K. Adcox et al.. Phys. Rev. Lett. 88 (2002) 242301.

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