Production of Lambda, Cascade and Omega Hyperons in ppbar Collisions at1.96 TeV Center of Mass Energy

0.23 MB·English

by  CDF Collaboration

Production of Λ0, Λ0, Ξ , and Ω Hyperons in pp Collisions at
1 ± ±
√s = 1.96 TeV
2
T. Aaltonen, E. Brucken, F. Devoto, P. Mehtala, and R. Orava
3
Division of High Energy Physics, Department of Physics,
4
University of Helsinki and Helsinki Institute of Physics, FIN-00014, Helsinki, Finland
5
1
1 B. A´lvarez Gonz´alezv, B. Casal, J. Cuevasv, G. Gomez, E. Palenciaf,
0 6
2
7 T. Rodrigo, A. Ruiz, L. Scodellaro, I. Vila, and R. Vilar
n
a
Instituto de Fisica de Cantabria, CSIC-University of Cantabria, 39005 Santander, Spain
J 8

5
1
S. Amerio, M. Baucecc, D. Bisellocc, G. Busettocc, G. Compostellacc, M. d’Erricocc,
9

]
x T. Dorigo, A. Gresele, I. Lazzizzera, D. Lucchesicc, and S. Pagan Grisocc
10
e
-
p 11 Istituto Nazionale di Fisica Nucleare, Sezione di Padova-Trento,
e
h ccUniversity of Padova, I-35131 Padova, Italy
12
[

1
v 13 D. Amidei, M. Campbell, A. Eppig, D. Mietlicki,
6
9 14 G.L. Strycker, M. Tecchio, A. Varganov, and T. Wright
9
2 University of Michigan, Ann Arbor, Michigan 48109, USA
15
.
1
0
1 16 A. Anastassov, M. Schmitt, and D. Stentz
1
: Northwestern University, Evanston, Illinois 60208, USA
v 17
i
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r 18 A. Annovi, M. Cordelli, P. Giromini, F. Happacher, M.J. Kim, F. Ptohosh, and S. Torre
a
Laboratori Nazionali di Frascati, Istituto Nazionale
19
di Fisica Nucleare, I-00044 Frascati, Italy
20
J. Antos, P. Bartos, A. Brisuda, R. Lysak, and S. Tokar
21
Comenius University, 842 48 Bratislava,
22
Slovakia; Institute of Experimental Physics, 040 01 Kosice, Slovakia
23
∗
G. Apollinari, J.A. Appel, W. Ashmanskas, W. Badgett, A. Beretvas, M. Binkley ,
24
B. Braua, K. Burkett, F. Canelli12, S. Carron, M. Casarsa, P. Catastini, G. Chlachidze,
25
F. Chlebana, M.E. Convery, R. Culbertson, D. Dagenhart, M. Datta, P. Dong,
26
∗
Deceased 1
J.C. Freeman, E. Gerchtein, C.M. Ginsburg, D. Glenzinski, A. Golossanov,
1
R.C. Group, S.R. Hahn, A. Hocker, W. Hopkinsg, E. James, S. Jindariani, T.R. Junk,
2
B. Kilminster, S. Lammel, J.D. Lewis, M. Lindgren, D.O. Litvintsev, T. Liu,
3
P. Lukens, R. Madrak, K. Maeshima, T. Miao, M.N. Mondragonk, R. Moore,
4
M.J. Morello, P. Movilla Fernandez, A. Mukherjee, P. Murat, J. Nachtmanm,
5
V. Papadimitriou, J. Patrick, A. Pronko, L. Ristori45, R. Roser, V. Rusu, P. Schlabach,
6
E.E. Schmidt, F.D. Snider, A. Soha, P. Squillacioti, J. Thomg, S. Tkaczyk, D. Tonelli,
7
D. Torretta, G. Velev, R.L. Wagner, W.C. Wester III, E. Wicklund, P. Wilson,
8
P. Wittichg, S. Wolbers, G.P. Yeh, K. Yim, J. Yoh, S.S. Yu, and J.C. Yun
9
Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
10
A. Apresyan, V.E. Barnes, D. Bortoletto, G. Flanaganr, A.F. Garfinkel, M. Jones,
11
A.T. Laasanen, Q. Liu, F. Margaroli, K. Potamianos, N. Ranjan, and A. Sedov
12
Purdue University, West Lafayette, Indiana 47907, USA
13
T. Arisawa, K. Ebina, N. Kimura, K. Kondo, J. Naganoma, and K. Yorita
14
Waseda University, Tokyo 169, Japan
15
∗
A. Artikov, J. Budagov, D. Chokheli, V. Glagolev, O. Poukhov ,
16
F. Prokoshiny, A. Semenov, A. Simonenko, A. Sissakian∗, and I. Suslov
17
Joint Institute for Nuclear Research, RU-141980 Dubna, Russia
18
J. Asaadi, A. Aurisano, A. Elagin, R. Eusebi, D. Goldin, T. Kamon, V. Khotilovich,
19
V. Krutelyovd, E. Lee, S.W. Leew, P. McIntyre, A. Safonov, D. Toback, and M. Weinberger
20
Texas A&M University, College Station, Texas 77843, USA
21
B. Auerbach, C. Cuenca Almenar, U. Husemann,
22
∗
S. Lockwitz, A. Loginov, M.P. Schmidt , and M. Stanitzki
23
Yale University, New Haven, Connecticut 06520, USA
24
F. Azfar, S. Farrington, C. Hays, J. Linacre, L. Oakes, and P. Renton
25
University of Oxford, Oxford OX1 3RH, United Kingdom
26
A. Barbaro-Galtieri, A. Cerrif, H.C. Fang, C. Haber,
27
2
C.-J. Lin, P. Lujan, J. Lys, J. Nielsene, and W.-M. Yao
1
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
2
B.A. Barnett, S. Behari, B. Blumenfeld, G. Giurgiu, P. Maksimovic, and M. Mathis
3
The Johns Hopkins University, Baltimore, Maryland 21218, USA
4
P. Barriaee, F. Bedeschi, G. Bellettinidd, M. Bucciantoniodd, R. Carosi,
5
V. Cavaliereee, G. Chiarelli, M.A. Ciocciee, F. Cresciolidd, M. Dell’Orsodd,
6
A. Di Cantodd, B. Di Ruzza, S. Donatidd, C. Ferrazzaff, P. Garosiee,
7
P. Giannetti, M. Giunta, G. Introzzi, S. Lami, G. Latinoee, S. Leodd, S. Leone,
8
A. Menzione, G. Piacentino, G. Punzidd, F. Ruffiniee, L. Sartori, A. Scribanoee,
9
F. Scuri, F. Sforzadd, M. Trovatoff, N. Turiniee, E. Vatagaff, and G. Volpidd
10
Istituto Nazionale di Fisica Nucleare Pisa, ddUniversity of Pisa,
11
eeUniversity of Siena and ffScuola Normale Superiore, I-56127 Pisa, Italy
12
G. Bauer, G. Gomez-Ceballos, M. Goncharov, K. Makhoul, and C. Paus
13
Massachusetts Institute of Technology,
14
Cambridge, Massachusetts 02139, USA
15
D. Beecher, I. Bizjakii, L. Cerritoq, M. Lancaster, E. Nurse, and D. Waters
16
University College London, London WC1E 6BT, United Kingdom
17
J. Bellinger, D. Carlsmith, W.H. Chung, M. Herndon,
18
J. Nett, L. Pondrom, J. Pursley, and V. Ramakrishnan
19
University of Wisconsin, Madison, Wisconsin 53706, USA
20
D. Benjamin, A. Bocci, S. Cabrerax, J. Dengc, A.T. Goshaw, B. Jayatilaka, A.V. Kotwal,
21
M. Kruse, S.H. Oh, T.J. Phillips, C. Wang, A. Wen, J. Yamaoka, G.B. Yu, and Y. Zeng
22
Duke University, Durham, North Carolina 27708, USA
23
A. Bhatti, L. Demortier, M. Gallinaro, K. Goulianos, G. Lungu, S. Malik, and C. Mesropian
24
The Rockefeller University, New York, New York 10065, USA
25
K.R. Bland, J.R. Dittmann, M.J. Frank, K. Hatakeyama,
26
3
S. Hewamanage, N. Krumnackl, and Z. Wu
1
Baylor University, Waco, Texas 76798, USA
2
C. Blocker and D. Clark
3
Brandeis University, Waltham, Massachusetts 02254, USA
4
A. Bodek, H.S. Budd, Y.S. Chung, P. de Barbaro,
5
J.Y. Han, K.S. McFarland, and W.K. Sakumoto
6
University of Rochester, Rochester, New York 14627, USA
7
J. Boudreau, K. Gibson, C. Liu, A. Rahaman, and P.F. Shepard
8
University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
9
A. Boveia, C. Grosso-Pilcher, M. Hurwitz, W. Ketchum, Y.K. Kim, D. Krop,
10
S. Kwang, H.S. Lee, S. Shiraishi, M. Shochet, J. Tang, S. Wilbur, and U.K. Yangp
11
Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, USA
12
L. Brigliadoribb, A. Castrobb, M. Deninno, M.K. Jha, P. Mazzanti,
13
N. Moggi, M. Mussinibb, F. Rimondibb, and S. Zucchellibb
14
Istituto Nazionale di Fisica Nucleare Bologna,
15
bbUniversity of Bologna, I-40127 Bologna, Italy
16
C. Bromberg, M. Campanelli, Z. Gunay-Unalan, M. Hussein, J. Huston, and K. Tollefson
17
Michigan State University, East Lansing, Michigan 48824, USA
18
S. Budd, B. Carls, D. Errede, S. Errede, H. Gerberich, M.S. Neubauer,
19
O. Norniella, K. Pitts, E. Rogers, A. Sfyrla, and G.A. Thompson
20
University of Illinois, Urbana, Illinois 61801, USA
21
P. Bussey, A. Robson, and R. St. Denis
22
Glasgow University, Glasgow G12 8QQ, United Kingdom
23
A. Buzatu, N. Hussain, P. Sinervo, B. Stelzer, O. Stelzer-Chilton, and A. Warburton
24
Institute of Particle Physics: McGill University, Montr´eal,
25
Qu´ebec, Canada H3A 2T8; Simon Fraser University, Burnaby,
26
4
British Columbia, Canada V5A 1S6; University of Toronto,
1
Toronto, Ontario, Canada M5S 1A7; and TRIUMF,
2
Vancouver, British Columbia, Canada V6T 2A3
3
C. Calancha, J.P. Fernandez, O. Gonz´alez, R. Mart´ınez-Ballar´ın,
4
I. Redondo, P. Ttito-Guzm´an, and M. Vidal
5
Centro de Investigaciones Energeticas Medioambientales
6
y Tecnologicas, E-28040 Madrid, Spain
7
S. Camarda, M. Cavalli-Sforza, G. De Lorenzo, C. Deluca,
8
S. Grinstein, M. Mart´ınez, L. Ortolan, and V. Sorin
9
Institut de Fisica d’Altes Energies, Universitat Autonoma de Barcelona,
10
E-08193, Bellaterra (Barcelona), Spain
11
A. Canepa, J. Heinrich, J. Keung, J. Kroll, E. Lipeles, N.S. Lockyer, C. Neuz, E. Pianori,
12
T. Rodriguez, E. Thomson, Y. Tu, P. Wagner, D. Whitesonc, and H.H. Williams
13
University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
14
S. Carrillok, R. Field, I. Furic, N. Goldschmidt, S. Klimenko,
15
J. Konigsberg, A. Korytov, I. Oksuzian, A. Sukhanov, and F. V´azquezk
16
University of Florida, Gainesville, Florida 32611, USA
17
D. Cauz, C. Pagliarone, G. Paulettahh, A. Penzo,
18
M. Rossi, L. Santihh, P. Totarohh, and A. Zanetti
19
Istituto Nazionale di Fisica Nucleare Trieste/Udine,
20
I-34100 Trieste, hhUniversity of Trieste/Udine, I-33100 Udine, Italy
21
Y.C. Chen, S. Hou, A. Mitra, P.K. Teng, and S.M. Wang
22
Institute of Physics, Academia Sinica,
23
Taipei, Taiwan 11529, Republic of China
24
M. Chertok, J. Conway, C.A. Cox, D.J. Cox, R. Erbacher, R. Forrest, A. Ivanovo,
25
W. Johnson, R.L. Lander, D.E. Pellett, T. Schwarz, S.Z. Shalhout, and J.R. Smith
26
University of California, Davis, Davis, California 95616, USA
27
5
K. Cho, E.J. Jeon, K.K. Joo, D.H. Kim, H.S. Kim, H.W. Kim, J.E. Kim, S.B. Kim,
1
D.J. Kong, J.S. Lee, C.S. Moon, Y.D. Oh, S. Uozumi, Y.C. Yang, and I. Yu
2
Center for High Energy Physics: Kyungpook National University,
3
Daegu 702-701, Korea; Seoul National University, Seoul 151-742,
4
Korea; Sungkyunkwan University, Suwon 440-746,
5
Korea; Korea Institute of Science and Technology Information,
6
Daejeon 305-806, Korea; Chonnam National University, Gwangju 500-757,
7
Korea; Chonbuk National University, Jeonju 561-756, Korea
8
J.P. Chou, M. Franklin, J. Guimaraes da Costa, and S. Moed
9
Harvard University, Cambridge, Massachusetts 02138, USA
10
C.I. Ciobanu, M.Corbo, N. d’Ascenzot, N. Ershaidataa, V. Savelievt, and A. Savoy-Navarro
11
LPNHE, Universite Pierre et Marie Curie/IN2P3-CNRS, UMR7585, Paris, F-75252 France
12
A. Clark, J.E. Garcia, A. Lister, and X. Wu
13
University of Geneva, CH-1211 Geneva 4, Switzerland
14
S. De Cecco, S. Giagugg, M. Iorigg, P. Mastrandrea, and M. Rescigno
15
Istituto Nazionale di Fisica Nucleare, Sezione di Roma 1,
16
ggSapienza Universit`a di Roma, I-00185 Roma, Italy
17
M. D’Onofrio, G. Mancab, R. McNultyi, A. Mehta, and T. Shears
18
University of Liverpool, Liverpool L69 7ZE, United Kingdom
19
M. Feindt, M. Heck, D. Horn, M. Kreps, T. Kuhr, J. Lueck,
20
C. Marino, J. Morlock, Th. Muller, A. Schmidt, and F. Wick
21
Institut fu¨r Experimentelle Kernphysik,
22
Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany
23
J. Galyardt, D. Jang, S.Y. Jun, M. Paulini, E. Pueschel, J. Russ, and J. Thome
24
Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
25
V. Giakoumopoulou, N. Giokaris, A. Manousakis-Katsikakis, and C. Vellidis
26
6
University of Athens, 157 71 Athens, Greece
1
M. Gold, I. Gorelov, S. Seidel, J. Strologas, and M. Vogel
2
University of New Mexico, Albuquerque, New Mexico 87131, USA
3
E. Halkiadakis, D. Hare, D. Hidas, A. Lath, and S. Somalwar
4
Rutgers University, Piscataway, New Jersey 08855, USA
5
A. Hamaguchi, Y. Katon, T. Okusawa, Y. Seiya,
6
T. Wakisaka, K. Yamamoto, and T. Yoshidaj
7
Osaka City University, Osaka 588, Japan
8
K. Hara, S.H. Kim, M. Kurata, H. Miyake, Y. Nagai, K. Sato, M. Shimojimas,
9
Y. Sudo, K. Takemasa, Y. Takeuchi, T. Tomura, and F. Ukegawa
10
University of Tsukuba, Tsukuba, Ibaraki 305, Japan
11
M. Hare, A. Napier, S. Rolli, K. Sliwa, and B. Whitehouse
12
Tufts University, Medford, Massachusetts 02155, USA
13
R.F. Harr, P.E. Karchin, and M.E. Mattson
14
Wayne State University, Detroit, Michigan 48201, USA
15
R.E. Hughes, K. Lannonu, J. Pilot, J.S. Wilson, B.L. Winer, and H. Wolfe
16
The Ohio State University, Columbus, Ohio 43210, USA
17
T. LeCompte, L. Nodulman, A.A. Paramonov, and A.B. Wicklund
18
Argonne National Laboratory, Argonne, Illinois 60439, USA
19
I. Nakano
20
Okayama University, Okayama 700-8530, Japan
21
C. Plager and R. Wallny
22
University of California, Los Angeles,
23
Los Angeles, California 90024, USA
24
I. Shreyber
25
7
Institution for Theoretical and Experimental Physics, ITEP, Moscow 117259, Russia
1
2 (Dated: January 18, 2011)
Abstract
We report a set of measurements of inclusive invariant p differential cross sections of Λ0, Λ0,
T
± ±
Ξ , and Ω hyperons reconstructed in the central region with pseudorapidity η < 1 and p up
T
| |
to 10 GeV/c. Events are collected with a minimum-bias trigger in pp¯collisions at a center-of-mass
energy of 1.96 TeV using the CDF II detector at the Tevatron Collider. As p increases, the slopes
T
of the differential cross sections are similar not only to each other but also to those of mesons,
which could indicate a universality of the particle production in p The invariant differential cross
T
sections are also presented for different charged-particle multiplicity intervals.
8
Ever since their discovery in cosmic ray interactions [1], particles containing strange
1
quarkshavebeenextensively studiedatparticlecolliders(e+e− [2], ep[3],pp¯[4,5]andpp[6]).
2
The process by which hadrons in general are produced from interactions is an unsolved
3
problem in the standard model, and a detailed analysis of production properties of particles
4
with different quark flavors and numbers of quarks could pave the way to understanding the
5
process from first principles. The data on strange particle production can also be used to
6
refine phenomenological models and set parameters, such as the strange quark suppression
7
constant in event generators, which have become an integral part of any data analysis.
8
Interest in particles containing strange quarks increased with the introduction of the quark-
9
gluon plasma (QGP). Formation of quark-gluon plasma in a collision could manifest itself as
10
an enhanced production of strange particles such as kaons and hyperons [7]. To isolate QGP
11
signatures in heavy-ion collision data, understanding the particle production properties from
12
simple nucleon interactions is necessary.
13
Thereareampledataontheproductionofparticleswithonestrangequark, butverylittle
14
available on particles with two or more [8, 9]. Previous studies of hyperons from colliders
15
such as RHIC [10], SppS [11], and the Tevatron [12, 13] were limited by low sample statistics
16
and the limited accessible range of hyperon momentum component transverse to the beam
17
direction (p ). In this Letter, we report on a study of the hyperons Λ0 (quark content uds),
18 T
Ξ− (dss), and Ω− (sss) and their corresponding antiparticles (Λ0, Ξ+, and Ω+). For these
19
hyperons, the inclusive invariant p differential cross sections are measured up to p of 10
20 T T
GeV/c, based on 100 million minimum-bias events collected with the CDF II detector.
21
∼
The measurements reported here are the current best from any hadron collider experiment
22
in terms of statistics and p range.
23 T
The CDF II detector is described in detail elsewhere [14]. The components most relevant
24
to this analysis are those that comprise the tracking system, which is within a uniform axial
25
magnetic field of 1.4T. The inner tracking volume is composed of a system of eight layers of
26
silicon microstrip detectors ranging in radius from 1.5 to 28.0 cm [15] in the pseudorapidity
27
region η < 2 [16]. The remainder of the tracking volume is occupied by the Central Outer
28
| |
Tracker (COT). The COT is a cylindrical drift chamber containing 96 sense-wire layers
29
grouped in eight alternating superlayers of axial and stereo wires [17]. Its active volume
30
covers 40 to 140 cm in radius and z < 155 cm. The transverse-momentum resolution of
31
| |
tracks reconstructed using COT hits is σ(p )/p2 0.0017/(GeV/c).
32 T T ∼
9
Events for this analysis are collected with a “minimum-bias” (MB) trigger, which selects
1
beamcrossingswithatleastonepp¯interactionbyrequiringatimingcoincidenceforsignalsin
2
bothforwardandbackwardgasCherenkov counters [18]covering theregions3.7 < η < 4.7.
3
| |
TheMBtriggerisrate-limitedtokeepthefinaltriggeroutputat1Hz. Primaryeventvertices
4
are identified by the convergence of reconstructed tracks along the beam axis. Events are
5
accepted that contain a reconstructed vertex in the fiducial region z 60 cm centered
6 vtx
| | ≤
around the nominal CDF origin (z = 0). When an event has more than one vertex, the
7
highest quality vertex, usually the one with the most associated tracks, is selected and it
8
is required that there be no other vertices within 5 cm of this vertex. This selection
9
±
introduces a bias toward high multiplicity events as the instantaneous luminosity increases.
10
To combine events collected at different average instantaneous luminosities, we determine a
11
per-event weight as a function of the charged-track multiplicity N in order to match the
12 ch
multiplicity distribution of a data sample where the average number of interactions is less
13
than 0.3 per bunch crossing. For the N calculation, tracks are required to have a high
14 ch
track-fit quality with χ2 per degree-of-freedom (χ2/dof) less than 2.5, and more than five
15
hits in at least two axial and two stereo COT segments. It is further required that tracks
16
satisfy η < 1, impact parameter d [19] less than 0.25 cm, the distance along the z-axis
17 0
| |
(δZ )between the event vertex and the track position at the point of closest approach to the
18 0
vertex in the r φ plane be less than 2 cm, and p > 0.3 GeV/c. The p selection is to
19 T T
−
minimize the inefficiency of the track-finding algorithm for low momentum tracks.
20
We search for Λ0 pπ− decays using tracks with opposite-sign charge and p > 0.325
21 T
→
GeV/c that satisfy the χ2/dof and COT segment requirements. In this Letter, any reference
22
to a specific hyperon state implies the antiparticle state as well. For each two-track combi-
23
nation we calculate their intersection coordinate in the r φ plane. Once this intersection
24
−
point, referred to as the secondary vertex, is found, the z-coordinate of each track (Z and
25 1
Z ) is calculated at that point. If the distance Z Z is less than 1.5 cm, the tracks are
26 2 1 2
| − |
considered to originate from a Λ0 candidate decay. The pair is traced back to the vertex and
27
we require δZ be less than 2 cm, and the d be less than 0.25 cm. To reduce backgrounds
28 0 0
29 further, we require the Λ0 decay length LΛ0, the distance in the r φ plane between the
−
primary and secondary vertices, to be greater than 2.5 cm and less than 50 cm.
30
The invariant mass M of the two-track system is calculated by attributing the proton
31 pπ
mass to the track with the higher p , as preferentially expected by the kinematics of a Λ0
32 T
10