Fermi National Accelerator Laboratory Measurement of the Isolated Prom t Photon Cross Section inpp Collisions at 1p s=1.8 TeV The CDF Collaboration Fermi National Accelerator Laboratory P.O. Box 500, Batavia, Illinois 60510 February 1992 Submitted to Physical Reuiew Letters. +operatedbyu. nrversiSesResearch A-ssxiation Inc. under Cmtmct No. DE-ACM-76CHCNOOO tilh tie United States bpatbnent of Energy
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Fermi National Accelerator Laboratory
Measurement of the Isolated Prom t Photon Cross Section inpp Collisions at 1p s=1.8 TeV
The CDF Collaboration
Fermi National Accelerator Laboratory P.O. Box 500, Batavia, Illinois 60510
February 1992
Submitted to Physical Reuiew Letters.
+operatedbyu. nrversiSes Research A-ssxiation Inc. under Cmtmct No. DE-ACM-76CHCNOOO tilh tie United States bpatbnent of Energy
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accumcy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specifti commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein da not necessarily state or reflect those of the United States Government or any agency thereof,
FERMILAB-PUB-92/31-E CLlF/PUB/.JET/CDFR/1516
Measurement of the Isolated Prompt Photon Cross Section
in fip Collisions at fi = 1.8 TeV
F. Abe,(‘) D. Amidei, G. Apollinari, (*‘V M. Atac,(*) P. Au~bincloss,(‘~) A. R. Bade@)
N. Bacchetta$“) M. W. Bailey,(“) A. Bamberger,(*“) P. de Barbam, B. A. B.m,ett,@)
A. Barbam-Galtieri,(‘O) V. E. Barnes,@*) T. Bauma~,(~) F. Bedescbi,(l3) S. Behrends,(*l
S. Belforte,(13) G. Bellettini,(13) J. Bellinger,(zll D. Benjmnin,(ao) J. Bensinger,
A. Beretvas,(‘l J. P. Berge,(*) S. Bertolucci,(6) S. Bha&a,(‘) M. Bb&ley,(*) D. Blsello,(l’l
R. Blair,(‘) C. Blocker,(‘) A. Bodek,(15) V. Bolognesi,(13) A. W. Booth,(*) C. Boswell,(a)
G. Brandenburg,(e) D. Brown,(e) E. Buckley-Gee+‘) H. S. Budd,(lS) G. Busetto,(“)
A. Byon-Wagner,(‘) K. L. Byrun,(211 C. Campagnari,(3) M. Campbell,(3) A. Caner,(*)
R. Carey,(e) W. Carithers,(lo) D. Carlsmith,(21) J. T. Carroll,(*) R. Ca&more,(*@)
A. Castro,(“) F. Cer~elli,(‘~) K. Chadwick,(*) G. ChiarelX,(s) W. Chinowsky,(‘ol
S. Cihangir,(‘) A. G. Clark,(*) M. Cobal,(131 D. C onnor,@) M. Contrerasf’) J. Cooper,(*)
M. Cordelli,@) D. C rane,(*) M. Cwatolc@ C. Day,(*) F. DeJongh,(*) S. Dell’Agnello,(13)
M. Dell’Orsc~,(‘~l L. Demortier,(a) B. Denby, P. F. Denvent,@) T. De&n,(“)
D. DiBitonto,(18) M. Dickson,(15) R. B. Drucker,(‘o) K. Einsweiler,(lo) J. E. El&,(*)
R. Ely,(“) S. Eno,c3) S. Errede,(‘l B. Esposito,(61 A. Etchegoyen,(*+) B. Flaugher,(*)
G. W. Foster,(*) M. l?rankli11,(~1 J. Freeman,(*) H. Frisch,(3) ‘7. Fuess,(*l y. F&$(Q)
A. F. Gafinkel,(‘*) A. Gautbier,c7) S. Geer,(*l D. W. Gerdes,t3) P. Gi-etti,(‘al
N. Giokaris,(‘e) P. Giromini,@‘) L. Gladney,(lz) M. Gold,@) K. Gotiaos,(le)
Submitted to Physical Review Letters, FebTuary 3, 1992.
II. Grassmann, J. Grieco,(13) C. Grosso-Pilcher,@) C. H&x,(10) S. Il. Hahn,c4)
Il. Handler,(21) K. Hara,(“) B. Hamal, R. M. Harris,(*) J. Hauser,c4) C. Hawk{‘71
T. HessinS, R. Hollebeek,(12) L. Holloway,(‘) P. Hu,(‘~) B. Hubbard,(1o)
B. T. H&mn,(‘*) R. Hughes,(12) P. Hurst,@) J. Huth,@) J. Hylen,(4) M. Imgli,(13)
T. Ino,@) H. Iso,@) H. Jensen, C. P. Jessop,@‘) R. P. Johmon,t4) U. Jo&,@)
R. W. Kadel,(“‘) T. K-on,(“) S. Kanda,(“) D. A. Kardelis,(7) I. Karliner,(7)
E. Kearn~,(~) L. Keeble,(‘*) R. Kephart,(‘) P. K es t en,(‘) R. M. Kemp, H. Keutelian,(4)
D. Kim,t4) S. Kim,@“) L. Kirsch,(‘) K. Kondo,@) J. Konigsberg,(~) E. Kovacs,(4)
S. E. Kuhlmann,(l~ E. Ku+‘) A. T. L aasanen,(“) J. I. Lam~ureux,(~*) S. Leom@
J. Lewis,(‘) W. Li,(‘) P. Limon,c4) T. M. Liss,(‘) N. Lockyer,(‘a) M. Loret& E. Low,(l2)
C. B. Luchini,(‘) P. Lukens,@) P. Maas, K. Maeshim=+) M. Mmgmo,(‘3)
J. P. Mariner,(‘) M. Mariotti,(13) R. Markeloff,(zl) L. A. Markosky,@) R. Mattb&,(z)
P. Mclntyre,(“) A. Menzione,@) T. Meyer,(‘s) S. Mikamo,@) M. Miller,@) T. Mima&,(*g)
S. Miscetti,@) M. Mishina,@) S. Miyashita,(lg) Y. Morita,(ls) S. Moulding,(z) J.
Mueller,(“) A. Mukherjee,(4) L. F. Nakae,@) I. N&mo,(le) C. Nelson,
C. Newman-Hol~nes,(~) J. S. T. Ng,@) M. N’ mnomiya,(‘*) L. Nodulman,@) S. Ogawa,(19)
R. Paoletti,(13) V. Papadimitriou,(4) A. Para, E. Pare,(B) S. Park,(*) J. P&r&,(4)
G. PaUletta,(13) L. Pescara,(“) T. J. PhilIips,(B) F. Ptohos,cB) R. Pl&&t,(*l
L. Pondrom,(“) J. Proudfoot, G. Punai,(13) D. Quade,(*) K. Ragan,(*2) G. R&inger,(3)
J. Rhoades,(“) M. Roach,(“) F. R.imondi,(‘,‘) L. Ristori,(‘s) T. Rod&go,(*) T. R&dy,(**)
A. R~odman,(~) W. K. Sakumoto,(16) A. Sansoni,(6) R. D. Sard,(‘) A. Savoy-Navarro,(4)
2
V. Scarpine, P. Schlabach,@) E. E. Schmidt,(*) 0. Sclmeider,(‘“) M. H. Schub,(‘*)
R. Schwitters,(B) A. Scribano,(13) S. Segler,(*) Y. Seiya,@) M. Shapiro,(lO) N. M. Shaw,(l*)
M. She&(‘*) M. Shochet,(3) J. Siegrist, 0’) P. Sinervo,(‘2) J. Skarha,(‘) K. Sliwa,@“)
D. A. Smith,(*3) F. D. Snider,@) L. Song, (la) M. Spahn,(‘“) P. Sphicas,@) R. St. D&s,@)
A. Stefanini,(13) G. Sullivan,@) R. L. Swartz, Jr.,c7) M. Taka~o,(‘~) F. Tartarelli,(*3)
K. Takikawa,(*‘) S. Tarem, D. Theriot, M. Timko,(le) P. Tipton, S. Tkaczyk,(*)
A. Toll&up,(*) J. Ton&on, (**) W. ‘lXschuk,(@) N. Turini,(13) Y. Tsay,@) F. Ukegawa,(*s)
D. Underwood,(‘) S. Vejcik, III,@) R. Vidal,(*) R. G. Wagner,(*) R. L. Wagner,(*)
N. Waim@ J. Walsh,(=) T. Watts,(*‘) R. Webb,@*) C. Wendt,@‘) H. Wenzel,(-)
W. C. Water, III,(“‘) T. Westhusing, (13) S. N. White,@‘) A. B. Wicklund,
H. H. Williams,(*z) B. L. Winer,@) J. Wyss, (**) A. Yagil,c4) K. Yasuoka,(*B) G. P. Yeh,(*)
J. Yoh,(‘) M. Yokoyama,(‘@) J. C. Yun,(*) A. Zanetti,(*3) F. Zetti,(*3) S. Zucchelli (*,a)
The CDF Collaboration
* A7gonn. National L.b.dOry, Argonne, minoi, so,99
3.16 x lo3 1.55 x 10s 1.03 x 103 4.36 x 10’ 1.91 x 102 1.30 x 102 1.13 x 101 7.15 x 10’ 6.98 x lo1 3.78 x lo1 2.23 x lo1 6.05 x 10’ 1.19 x 101 6.53 x 10” 2.22 x loo
‘ Stat.
w 11 12 13 18 22 12 12 12 11 20 20 15 37 41 79
jys.
(%) 21 13
6 2
12 23 26 32 40 50 71
7 6 6 8
14
0.75 I 1.25
Figure 1: a) The invariant mass of two photons frommeson decays (points), a two gaussian
plus background fit (solid), the polynomial-like background (dashes), and the expected
background from misidentified single photons (dots). b) The invariant mass of a neutral
cluster and charged track (points) compered to a Breit-Wigner plus background fit (solid)
and a polynomial background (dashes). c) The 2s distribution of photons (triangles) from q
decays in a), and of ?y”s (circles) from p decays in b), are compared to a detector simulation
(curves).
15
W 0 LL
kl
--
‘b --
EY A A
4 -- --
~ot”“““““““““““““1 10 20 30 40 50 60
fT (GeV/c)
Figure 2: a) The efficiency of photon candidates (points), and simulated photons and
background (solid curves) with systematic bounds (dashed curves) for the profile method
(circles) and the conversion method (triangles). The bounds on l , and q, are completely
correlated within each method. b) The i’ distribution of data (points) with PT < 27 GeV/c
compared to our simulation of photons (dots), background (dashes), and their sum (solid).
16
103
- s 102 s \ a a
a+ 7 b N
-0 loo
‘r CDF & = 1.8 TeV CDF X& = 1.8 TeV (NORM. UNCERTAINTY) (NORM. UNCERTAINTY)
n UA2 Js =630 GeV GeV
- QCD x
- QCD
10-l z- NLO, KMRS-B,, p=PT
\ I I I I I I I I I I I I I I III III
20 40 60 80
PT (GeVk)
Figure 3: The isolated prompt photon cross section, from both CDF (circles and trian-
gles) and UA2 [7] (squares), is compared to recent QCD predictions (cuws). The profile
method (circles) and conversion method (triangles) have separate normal.ieation uncertain-
ties shown in the legend. The next to leading order (NLO) predictions [5] use current parton
distributions (KMRS-& [6]) and a standard renormalization scale (p = PT).