Development and testing of novel stripixel detectors for the silicon vertex tracker at PHENIX

As a part of the upgrades for the PHENIX detector at RHIC,a silicon vertex tracking detector is planned. This detector will consist of two pixel layers followed by two strip-pixel layers in the barrel region,an d four mini-strip layers in the endcap region. As a part of the development phase of the vertex detector, we have set up three sensor testing facilities at Brookhaven National Laboratory, at State University of New York, Stonybrook, and at University of New Mexico to characterize the preproduction sensors, and develop our testing and quality assurance plans. Preliminary results from these test are presented here. Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

Silicon-tungsten calorimeter for the forward direction in the PHENIX experiment at RHIC

The PHENIX detector at RHIC has been designed to study hadronic and leptonic signatures of the Quark Gluon Plasma in heavy ion collisions and spin dependent structure functions in polarized proton collisions. The baseline detector measures muons in two muon spectrometers located forward and backward of mid-rapidity, and measures hadrons, electrons, and photons in two central spectrometer arms, each of which covers 90. in azimuth and 0.35 units of rapidity. Further progress requires extending rapidity coverage for hadronic and electromagnetic signatures by upgrading the functionality of the PHENIX muon spectrometers to include photon and jet measurement capabilities. Tungsten calorimeters with silicon pixel readout and fine transverse and longitudinal segmentation are proposed to attain this goal. The use of such a design provides the highest density and finest granularity possible in a calorimeter. for the PHENIX Forward Calorimeter Collaboration Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

A high-performance silicon tracker for the Compressed Baryonic Matter experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment is a fixed-target heavy-ion experiment planned at GSI's future international Facility for Antiproton and Ion Research (FAIR). CBM will study strongly interacting matter at high baryon densities where the QCD phase diagram is poorly known. The experiment applies a detector concept new to heavy-ion physics: All charged particles as well as secondary vertices from heavy-flavor decays are exclusively reconstructed in a high-performance silicon tracking system. It will be installed in a magnetic dipole field between the target and further detection systems for particle identification and calorimetry. High track densities and high collision rates require the application of most advanced silicon detectors. The technological challenges include high position resolution in thinnest possible pixel and microstrip sensors, combined with extreme radiation hardness, fast self-triggered readout and ultra low-mass mechanical supports. The article outlines the physics and detector concept of CBM and discusses the performance requirements of the silicon tracker and the beginning R&D. for the CBM collaboration Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

The Forward Vertex upgrade detector for PHENIX

The PHENIX detector at RHIC has been built with a strong heavy quark particles identification capability. These unique probes of matter are essential to adequately understand in-medium energy loss and to test the basic properties of QCD. The current PHENIX heavy flavor physics program will be significantly enhanced by the addition of the Forward Silicon Vertex upgrade detector (FVTX) in the acceptance of the existing muon arm detectors (1.2<|y|<2.4). The proposed tracker is planned to be put into operation in FY2011. Each arm of the FVTX detector consists of 4 disks of silicon strip sensors combined with FPHX readout chips and provides a precision measurement of the radial coordinate of the track. The current status of the detector design and construction and expectations for the physics signal extraction will be presented.     

A fast muon trigger for the PHENIX forward spectrometer upgrade

The PHENIX forward upgrade adds nosecone calorimeters and level-1 trigger (LVL-1) detectors to the muon forward spectrometers. The muon detector will trigger on high pT muons from W decay and reject background. This will enable study of quark and anti-quark polarizations in the proton. The upgrade will add momentum and timing information to the present muon trigger. Signals from 3 Resistive Plate Chambers (RPCs) will provide momentum and timing information for the LVL-1 trigger. Each RPC carries a plane with coarse structure to establish a space point for timing and one with radial cathode strips for azimuthal resolution. Timing resolution of ≈ 2 ns rejects beam-related backgrounds and tracking from RPCs minimizes muons from hadron decays. RPC information is sent by optical. bers to LVL-1 trigger processors. A discussion of physics measurements possible, layout of the upgrade and details of RPC design and tests are given below. for the PHENIX collaboration Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

The PHENIX forward spectrometer upgrade

The forward spectrometer upgrade of the PHENIX detector aims to add capabilities at forward rapidities to: probe nucleon structure through W production and promptphotons in polarized p + p, study nucleon structure in nuclei at high parton densities in p + A collisions through the measurement of γ and π⁰ in the forward region, greatly extend the acceptance for high p _T γ-jet measurements (jet tomography) in A + A, and increase our capabilities to measure the production quarkonium states by giving sensitivity to the χ _c through the J/ψ + γ channel. for the PHENIX Forward Upgrade Collaboration Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

First measurement of J/ψ anisotropy by PHENIX experiment at RHIC

Understanding the J/ψ suppression and possible recombination mechanisms at RHIC is one of the outstanding challenges for theorists and experimentalists. Recent results provided by PHENIX showed a stronger suppression at forward rapidity, while at mid-rapidity the suppression is similar to lower energy collision experiments. A large sample of Au + Au collisions at $ \sqrt {s_{NN} } $ \sqrt {s_{NN} } = 200 GeV was collected in 2007 with the PHENIX experiment at RHIC. Using this sample, J/ψs were identified in the di-electron decay channel. In order to probe the charm coalescence as an additional J/ψ production mechanism at RHIC, we studied the first determination of its v ₂ elliptic flow parameter at mid-rapidity.     

RHIC polarized proton status and plan

The Relativistic Heavy Ion Collider (RHIC) as the first high energy polarized proton collider has been providing collisions at a beam energy of 100 GeV since 2001. Equipped with two full Siberian snakes in each ring, polarization is preserved during the acceleration from injection to 100 GeV with careful control of the betatron tunes and the vertical orbit distortions. In the latest RHIC polarized proton run in 2006, a peak luminosity of 28 × 10³⁰cm⁻² s⁻¹ with 60% average polarization at store was achieved. During the run, RHIC also demonstrated its capability in providing a combination of polarized proton collisions with longitudinal polarization and radial polarization were provided to the STAR experiment and PHENIX experiment with the local spin rotators installed on either side of the STAR detector and PHENIX detector. Polarized protons were also first accelerated to 250 GeV at the end of RHIC 2006 run with a 46% polarization measured at this new store energy in one of the RHIC accelerators. Currently, the luminosity in RHIC is limited by the beam-beam effect. The plan is to triple the luminosity. Plans to achieve polarized proton collision at 250 GeV are also reported.     

Extending physics capabilities of the PHENIX detector with calorimetry at forward rapidities

The PHENIX detector at RHIC has been designed to study different signatures of the states of matter created in heavy-ion collisions, and to investigate the spin structure of the nucleon. The PHENIX detector measures muons in two muon spectrometers, located at forward rapidities (1.2 < |η| < 2.4) and hadrons, electrons and photons in the two central spectrometers at midrapidity (|η| <0.35). To make a next step in the PHENIX research program, it is necessary to extend the rapidity coverage beyond the limits set by the existing central spectrometer. The functionality of the PHENIX muon detectors can be extended with added capabilities to measure photonic and hadronic jets. Tungsten calorimeters with silicon pixel readout and fine transverse and longitudinal segmentation are proposed to attain this goal. The proposed calorimeters will be located in the forward directions on either side of the PHENIX interaction point. In this talk we report on the studies of the functionality of the proposed calorimeters: the detector energy resolution, the jet reconstruction capabilities and the characteristics of pion rejection.     

Beam test performance of prototype assemblies for the ALICE Silicon Pixel Detector

The silicon pixel detector (SPD) comprises the two innermost layers of the inner tracking system oft he ALICE experiment at LHC. Prototype SPD assemblies have been tested in high-energy proton and pion beams at the CERN SPS. The method used for data analysis and the most relevant results in relation to detector performance are presented. Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005. On behalf of the Silicon Pixel Detector project in the ALICE Collaboration     

First results from RHIC-PHENIX

The PHENIX experiment consists of a large detector system located at the newly commissioned relativistic heavy ion collider (RHIC) at the Brookhaven National Laboratory. The primary goal of the PHENIX experiment is to look for signatures of the QCD prediction of a deconfined high-energy-density phase of nuclear matter quark gluon plasma. PHENIX started data taking for Au+Au collisions at √sNN=130 GeV in June 2000. The signals from the beam-beam counter (BBC) and zero degree calorimeter (ZDC) are used to determine the centrality of the collision. A Glauber model reproduces the ZDC spectrum reasonably well to determine the participants in a collision. Charged particle multiplicity distribution from the first PHENIX paper is compared with the other RHIC experiment and the CERN, SPS results. Transverse momentum of photons are measured in the electro-magnetic calorimeter (EMCal) and preliminary results are presented. Particle identification is made by a time of flight (TOF) detector and the results show clear separation of the charged hadrons from each other. For the PHENXI Collaboration The word PHENIX is the abbreviation of Pioneering High Energy Nuclear Interaction Experiment.     

Nucleus-nucleus collisions at ultra-relativistic energies: Status and prospects

Physics with ultra-relativistic heavy ions at three different accelerators SPS at CERN and AGS and RHIC at BNL is reviewed. The physics discussed ranges from global event characteristics through direct photon production, proton-proton correlation studies to Quark Gluon Plasma (QGP) phase trasition signatures via dileptonic, photonic and hadronic signals.Invited lecture given at the International School-Workshop Relativistic Heavy-Ion Physics, Prague (Czech Republic), 19–23 September 1994.Managed by Martin Marietta Energy Systems, Inc., under contract DE-AC05-84OR21400 with the U.S. Department of Energy.In conclusion, I have indicated that the RHIC project is well underway, and that the two major experiments planned for the facility, PHENIX and STAR, are being implemented with broad capabilities to address future exciting physics issues. A strong argument can be made that European groups should join the RHIC effort even with the advent of the LHC project at CERN. Aside from covering different energy regions, the two projects are shifted in time by over five years relative to each other, and RHIC is a machine dedicated to nucleus-nucleus studies, while the LHC will be available only on a limited basis.     

Pion production in dAu collisions at RHIC energy

We present our results on neutral pion (π⁰) production in pp and dAu collisions at RHIC energy. Pion spectra are calculated in a next-to-leading order (NLO) perturbative QCD-based model. The model includes the transverse component of the initial parton distribution (“intrinsic k_T”). We compare our results to the available experimental data from RHIC, and fit the data with high precision. The calculation tuned this way is repeated for the dAu collision, and used to investigate the interplay of shadowing and multiple scattering at RHIC. The centrality dependence of the nuclear modification factor shows a measurable difference between different shadowing parameterizations.     

Search for the onset of baryon anomaly at RHIC-PHENIX

The baryon production mechanism at the intermediate p_T (2–5 GeV/c) at RHIC is still not well understood. The beam energy scan data in Cu+Cu and Au+Au systems at RHIC may provide us a further insight on the origin of the baryon anomaly and its evolution as a function of . In 2005 RHIC physics program, the PHENIX experiment accumulated the first intensive low beam energy data in Cu+Cu collisions. We present the preliminary results of identified charged hadron spectra in Cu+Cu at and 62.4 GeV using the PHENIX detector. The centrality and beam energy dependences of (anti)proton to pion ratios and the nuclear modification factors for charged pions and (anti)protons are presented. PACS 25.75.Dw     

High-p t and jet physics from RHIC to LHC

The observation of the strong suppression of high-p t hadrons in heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) at BNL has motivated a large experimental program using hard probes to characterize the deconfined medium created. However, what can be denoted as “leading particle” physics accessible at RHIC presents some limitations which motivate at higher energy the study of much more penetrating objects: jets. The gain in center-of-mass energy expected at the Large Hadron Collider (LHC) at CERN will definitively improve our understanding on how the energy is lost in the system, opening a major new window of study: the physics of jets on an event-by-event basis. We will concentrate on the expected performance for jet reconstruction in ALICE using the EMCal calorimeter. (for the ALICE Collaboration) The text was submitted by the author in English.     

Charged-particle multiplicity at mid-rapidity in Au-Au collisions at relativistic heavy-ion collider

The particle density at mid-rapidity is an essential global variable for the characterization of nuclear collisions at ultra-relativistic energies. It provides information about the initial conditions and energy density reached in these collisions. The pseudorapidity densities of charged particles at mid-rapidity in AuAu collisions at √^s _NN = 130 and 200 GeV at RHIC (relativistic heavy ion collider) have been measured with the PHENIX detector. The measurements were performed using sets of wire-chambers with pad readout in the two central PHENIX tracking arms. Each arm covers one quarter of the azimuth in the pseudorapidity interval |η| < 035. Data is presented and compared with results from proton-proton collisions and nucleus-nucleus collisions at lower energies. Extrapolations to LHC energies are discussed.     

Parton energy loss at strong coupling and the universal bound

The apparent universality of jet quenching observed in heavy-ion collisions at RHIC for light and heavy quarks, as well as for quarks and gluons, is very puzzling and calls for a theoretical explanation. Recently, it has been proposed that synchrotron-like radiation at strong coupling gives rise to a universal bound on the energy of a parton escaping from the medium. Since this bound appears to be quite low, almost all of the observed particles at high transverse momentum have to originate from the surface of the hot fireball. Here I make a first attempt of checking this scenario against the RHIC data and formulate a “universal-bound model” of jet quenching that can be further tested at RHIC and LHC.     

Generation of complete events containing very high-<Emphasis Type="Italic">p</Emphasis><Subscript>T</Subscript> jets

The study of very high transverse-momentum jets will be an important issue at the LHC, in particular since the corresponding cross sections will be considerably larger than at RHIC energies. Jets are expected to provide information on QGP formation, due to the energy loss of fast partons in the medium. Jet cross sections can in principle be compared to simple pQCD calculations, based on the hypothesis of factorization. But often it is useful or even necessary to not only compute the production rate of the very high-p _T jets, but in addition the “rest of the event”. The proposed talk is based on recent work, where we try to construct an event generator—fully compatible with pQCD—which allows one to compute complete events, consisting of high-p _T jets plus all the other low p _T particles produced at the same time. Whereas in “generators of inclusive spectra” like Pythia one may easily trigger on high-p _T phenomena, this is not so obvious for “generators of physical events”, where in principle one has to generate a very large number of events in order to finally obtain rare events (like those with a very high-p _T jet). We shall discuss how we overcome these difficulties in the framework of the EPOS model.     

Medium effects on φ decays to dilepton and kaon-antikaon pairs in relativistic heavy ion reactions

We consider the role of rescattering of secondary kaons on the dilepton branching ratio of the φ-meson. In-medium mass modifications and broadening of kaons and φ-mesons are taken into account. We find in the framework of a Bjorken scenario for the time evolution of the expanding fireball that the φ yield from dimuons is moderately or at least only slightly enhanced compared to that from kaon-antikaon pairs. The relation to experimental yields measured by the NA49, NA50 and CERES Collaborations at CERN SPS and the PHENIX Collaboration at RHIC is discussed.     

QCD in the nuclear medium and effects due to Cherenkov gluons

The equations of in-medium gluodynamics are proposed. Their classical lowest-order solution is explicitly shown for a color charge moving with constant speed. For chromopermittivity larger than 1 it describes emission of Cherenkov gluons resembling results of classical electrodynamics. The values of the real and imaginary parts of the chromopermittivity are obtained from the fits to experimental data on the double-humped structure around the away-side jet obtained at RHIC. The dispersion of the chromopermittivity is predicted by comparing the RHIC, SPS, and cosmic-ray data. This is important for LHC experiments. Cherenkov gluons may be responsible for the asymmetry of dilepton mass spectra near ρ meson observed in the SPS experiment with excess in the low-mass wing of the resonance. This feature is predicted to be common for all resonances. The “color rainbow” quantum effect might appear according to higher-order terms of in-medium QCD if the chromopermittivity depends on color.