In this work, we describe a physics program at the Relativistic Heavy Ion Collider (RHIC) with tagged forward protons. The program started with the proton-proton elastic scattering experiment ...(PP2PP), for which a set of Rosman Pot stations was built. The PP2PP experiment took data at RHIC as a dedicated experiment at the beginning of RHIC operations. To expand the physics program to include non-elastic channels with forward protons, like Central Exclusive Production (CEP), Central Production (CP) and Single Diffraction DIssociation (SD), the experiment with its equipment was merged with the STAR experiment at RHIC. Consequently the expanded program, which included both elastic and inelastic channels became part of the physics program and operations of the STAR experiment. In this paper we shall describe the physics results obtained by the PP2PP and STAR experiments to date.
The PP2PP experiment is one of five experiments at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory, Long Island, New York. It is designed to measure the elastic ...scattering of protons at
s
= 50–500
GeV. The detector consists of silicon strip detectors mounted in Roman Pots and installed in the RHIC ring 60
m from the interaction region. During the engineering run of 2002 and physics run of 2003 the detectors were inserted as close as 15 mm from the proton beam. An overview of the experiment and details of the detector design and performance will be presented.
The first result of the pp2pp experiment at RHIC on elastic scattering of polarized protons at s=200 GeV is reported here. The exponential slope parameter b of the diffractive peak of the elastic ...cross section in the t range 0.010⩽|t|⩽0.019 (GeV/c)2 was measured to be b=16.3±1.6(stat.)±0.9(syst.) (GeV/c)−2.
Development and performance of a low-background
γ-ray spectrometer are described. The spectrometer consists of a 131% efficient Ge detector in U-type configuration. The passive shielding consists of ...ultrapure lead of 6″ thickness. A top muon guard is used as an active shielding. The spectrometer and shielding are positioned inside a steel room made of 6″-thick pre-World War II iron. The steel room is located underground with
33
m
of water-equivalent overburden. The total integrated background rate in the energy range 50–
2700
keV
was measured at
0.068
counts
per
second
per
100
cm
3
Ge volume. The spectrometer serves as a reference instrument for low-level and highly accurate environmental radioactivity measurements. One specific application of
228
Ra
determination in drinking water is described. With a
1
l
water sample, 1-step chemical procedure, and
1000
min
counting time, a detection limit
L
d=20
mBq/l
(0.55
pCi/l)
was reached, which meets the EPA mandated limit of
1
pCi/l
. Methods of upgrading the spectrometer as well as the predicted improvements in
228
Ra
detection, including direct counting of water without chemical processing, are discussed.
We present STAR measurements of strange hadron ( K S0, Λ , Λ ¯, Ξ -, Ξ ¯+, Ω -, Ω ¯+ , and Φ ) production at midrapidity ( |y|<0.5 ) in Au+Au collisions at sNN = 7.7–39 GeV from the Beam Energy Scan ...Program at the Relativistic Heavy Ion Collider (RHIC). Transverse-momentum spectra, averaged transverse mass, and the overall integrated yields of these strange hadrons are presented versus the centrality and collision energy. Antibaryon-to-baryon ratios ( Λ ¯/ Λ , Ξ ¯+/ Ξ -, Ω ¯+/ Ω - ) are presented as well and used to test a thermal statistical model and to extract the temperature normalized strangeness and baryon chemical potentials at hadronic freeze-out ( μB/Tch and μS/Tch ) in central collisions. Strange baryon-to-pion ratios are compared to various model predictions in central collisions for all energies. The nuclear modification factors ( RCP ) and antibaryon-to-meson ratios as a function of transverse momentum are presented for all collision energies. The K S0 RCP shows no suppression for pT up to 3.5 GeV/c at energies of 7.7 and 11.5 GeV. The Λ ¯/ K S0 ratio also shows baryon-to-meson enhancement at intermediate pT ( ≈2.5 GeV/c ) in central collisions at energies above 19.6 GeV. Lastly, both observations suggest that there is likely a change of the underlying strange quark dynamics at collision energies below 19.6 GeV.
PHENIX magnet system Aronson, S.H.; Bowers, J.; Chiba, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2003, Letnik:
499, Številka:
2
Journal Article
Recenzirano
The PHENIX magnet system is composed of three spectrometer magnets with warm iron yokes and water-cooled copper coils. The Central Magnet (CM) is energized by two pairs of concentric coils and ...provides a field around the interaction vertex that is parallel to the beam. This allows momentum analysis of charged particles in the polar angle range from 70° to 110°. The north and south Muon Magnets (MMN and MMS) use solenoid coils to produce a radial magnetic field for muon analysis. They each cover a pseudorapidity interval of 1.1–2.3 and full azimuth. The coils are wound on cylindrical surfaces at the end of large tapered pistons. Each of the three magnets provides a field integral of about
0.8
T
-m. The physical and operating parameters of the magnets and their coils are given along with a description of the magnetic fields generated. The geometric, thermal and magnetic analysis leading to the coil design is discussed. The magnetic volumes of the PHENIX magnets are very large and complex, so a new technique was developed to map the fields based on surface measurements of a single field component using single axis Hall probes mounted on a rotating frame. A discussion of the performance of the CM during the first year of PHENIX running is given.
We report the first results on differential, total and elastic cross sections
in proton-proton collisions at the Relativistic Heavy Ion Collider (RHIC) at
$\sqrt{s}=200$ GeV. The data lwere obtained ...with the Roman Pot Detector
subsystem of the STAR experiment. The data used for this analysis cover the
four-momentum transfer squared ~($t$) range $ 0.045 \le |t| \le 0.135$
(GeV/c)$^2$. The Roman Pot system was placed downstream of the STAR detector.
During the data taking the Roman Pots were moved to ~8$\sigma_{y}$, the
vertical distance of from the beam center. They were operated during standard
data taking procedure. The results include values of the exponential slope
parameter (B), elastic cross section ($\sigma_{el}$) and the total cross
section ($\sigma_{tot}$) obtained by extrapolation of the elastic differential
cross section ($d\sigma/dt$) to the optical point at $|t| = 0$ (GeV/c)$^{2}$.
The detector setup and analysis procedure are reviewed. All results are
compared with the world data.
We present the measurement of the transverse single-spin asymmetry of weak boson production in transversely polarized proton-proton collisions at s=500 GeV by the STAR experiment at RHIC. The ...measured observable is sensitive to the Sivers function, one of the transverse-momentum-dependent parton distribution functions, which is predicted to have the opposite sign in proton-proton collisions from that observed in deep inelastic lepton-proton scattering. These data provide the first experimental investigation of the nonuniversality of the Sivers function, fundamental to our understanding of QCD.
In this paper, we present results from a harmonic decomposition of two-particle azimuthal correlations measured with the STAR detector in Au + Au collisions for energies ranging from √sNN = 7.7 to ...200 GeV. The third harmonic v$2\atop{3}${ 2 } = <cos3(Φ1 - Φ)> , where Φ1 - Φ2 is the angular difference in azimuth, is studied as a function of the pseudorapidity difference between particle pairs Δη = η1-η2 . Nonzero v$2\atop{3}${ 2 } is directly related to the previously observed large- Δη narrow- ΔΦ ridge correlations and has been shown in models to be sensitive to the existence of a low viscosity quark gluon plasma phase. For sufficiently central collisions, v$2\atop{3}${ 2 } persist down to an energy of 7.7 GeV, suggesting that quark gluon plasma may be created even in these low energy collisions. In peripheral collisions at these low energies, however, v$2\atop{3}${ 2 } is consistent with zero. Finally, when scaled by the pseudorapidity density of charged-particle multiplicity per participating nucleon pair, v$2\atop{3}${ 2 } for central collisions shows a minimum near √sNN = 20 GeV .
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