arXiv subjects

Frank Simon

Publications and source records attributed to Frank Simon.

70 records · Page 4Linked to original sources

arXiv2009

Hadronic showers in the CALICE calorimeter prototypes

The CALICE collaboration has constructed highly granular electromagnetic and hadronic calorimeter prototypes to evaluate technologies for the use in detector systems at the future International Linear Collider. These calorimeters have been tested extensively in particle beams at CERN and at Fermilab. We present preliminary results of an analysis of hadronic events in the combined system under test at CERN in 2006 and 2007, comprising a SiW ECAL, a scintillator tile HCAL and a scintillator strip tail catcher, the latter two with SiPM readout. The properties of hadronic showers in the HCAL, compared to simulations performed with GEANT4, are discussed. Particular emphasis is placed on the study of the linearity of the detector response and on the single particle energy resolution achievable with simple weighting algorithms based on the local energy density in the hadronic showers.

physics.ins-det↗

arXiv2009

Track Segments in Hadronic Showers: Calibration Possibilities for a Highly Granular HCAL

The CALICE collaboration has constructed a highly granular hadronic calorimeter based on small scintillator tiles read out with silicon photomultipliers. With this detector, data was taken at CERN and at Fermilab. The high granularity of the detector allows the identification of minimum-ionizing track segments within hadronic showers, demonstrating the imaging capabilities of particle flow calorimeters. These tracks can be used for the cell-by-cell calibration of such a calorimeter. The possibility to calibrate a complete ILC calorimeter with such track segments in the absence of muons is also investigated.

physics.ins-det↗

arXiv2008

Calibration of a Highly Granular Hadronic Calorimeter with SiPM Readout

A highly granular hadronic calorimeter (HCAL) based on scintillator tiles with individual readout by silicon photomultipliers (SiPMs) has been constructed by the CALICE collaboration and has been tested extensively in particle beams at CERN. The 7608 SiPMs coupled to scintillator tiles in the approximately 1 cubic meter large calorimeter allow large sample studies of behavior of these devices under varying voltage and temperature as well as their saturation behavior. We also present detailed studies of the temperature dependence of the calorimeter signal in muon and hadron beams. The calibration of the full calorimeter using muons is discussed. In addition, a novel method for calibration and detector studies using minimum-ionizing track segments in hadronic showers, is explored.

physics.ins-det↗

arXiv2008

Beam Performance of Tracking Detectors with Industrially Produced GEM Foils

Three Gas-Electron-Multiplier tracking detectors with an active area of 10 cm x 10 cm and a two-dimensional, laser-etched orthogonal strip readout have been tested extensively in particle beams at the Meson Test Beam Facility at Fermilab. These detectors used GEM foils produced by Tech-Etch, Inc. They showed an efficiency in excess of 95% and spatial resolution better than 70 um. The influence of the angle of incidence of particles on efficiency and spatial resolution was studied in detail.

physics.ins-det↗

arXiv2008

Proton Driven Plasma Wakefield Acceleration

Plasma wakefield acceleration, either laser driven or electron-bunch driven, has been demonstrated to hold great potential. However, it is not obvious how to scale these approaches to bring particles up to the TeV regime. In this paper, we discuss the possibility of proton-bunch driven plasma wakefield acceleration, and show that high energy electron beams could potentially be produced in a single accelerating stage.

physics.acc-ph↗

arXiv2007

Triple GEM Detectors for the Forward Tracker in STAR

Future measurements of the flavor-separated spin structure of the proton via parity-violating W boson production at RHIC require an upgrade of the forward tracking system of the STAR detector. This upgrade will allow the reconstruction of the charge sign of electrons and positrons produced from decaying W bosons. A design based on six large area triple GEM disks using GEM foils produced by Tech-Etch Inc. has emerged as a cost-effective solution to provide the necessary tracking precision. We report first results from a beam test of three test detectors using Tech-Etch produced GEM foils and a laser etched two dimensional strip readout. The detectors show good operational stability, high efficiency and a spacial resolution of around 70 um or better, exceeding the requirements for the forward tracking upgrade. The influence of the angle of incidence of the particles on the spatial resolution of the detectors has also been studied in detail.

physics.ins-det↗

arXiv2007

The STAR Tracking Upgrade

The STAR experiment at the Relativistic Heavy Ion Collider RHIC studies the new state of matter produced in relativistic heavy ion collisions and the spin structure of the nucleon in collisions of polarized protons. In order to improve the capabilities for heavy flavor measurements and the reconstruction of charged vector bosons an upgrade of the tracking system both in the central and the forward region is pursued. The challenging environments of high track multiplicity in heavy ion collisions and of high luminosity in polarized proton collisions require the use of new technologies. The proposed inner tracking system, optimized for heavy flavor identification, is using active pixel sensors close to the collision point and silicon strip technology further outward. Charge sign determination for electrons and positrons from the decay of W bosons will be provide by 6 large-area triple GEM disks currently under development. A prototype of the active pixel detectors has been tested in the STAR experiment, and an extensive beam test of triple GEM detectors using GEM foils produced by Tech-Etch of Plymouth, MA has been done at Fermilab.

physics.ins-det↗

arXiv2007

Longitudinal Spin Measurements with Inclusive Hadrons in Polarized p+p Collisions at 200 GeV

We present measurements of the double longitudinal spin asymmetries for inclusive pi0 and pi+(-) production in polarized p+p collisions at sqrt(s) = 200 GeV at mid-rapidity with the STAR detector from the 2005 RHIC run. These measurements are used to access Delta G/G, the gluon polarization in the proton. The observed unpolarized inclusive cross sections show good agreement with NLO pQCD calculations. The double longitudinal spin asymmetries are compared to NLO pQCD calculations based on different assumptions for the gluon polarization in the nucleon to provide constraints on Delta G/G. At the present level of statistics the measured asymmetries disfavor a large positive gluon polarization, but cannot yet distinguish between other scenarios.

hep-ex↗

arXiv2006

Longitudinal Spin Asymmetry and Cross Section of Inclusive pi0 Production in Polarized p+p Collisions at RHIC

We present the first measurement of the cross section and the double longitudinal spin asymmetry of inclusive pi0 production in polarized p+p collisions at Sqrt(s) = 200 GeV at mid-rapidity with the STAR detector, using the barrel electromagnetic calorimeter. The measured cross section is compared to NLO pQCD calculations and can provide constraints on the pion fragmentation functions. Fragmentation is studied directly by measuring the momentum fraction of pi0 in jets, a quantity that is affected by the fragmentation process and jet reconstruction effects. The double longitudinal spin asymmetry is compared to NLO pQCD calculations based on different assumptions for the gluon polarization in the nucleon to provide constraints on delta g/g. At the present level of statistics the measured asymmetry disfavors a large positive gluon polarization, but can not yet distinguish between other scenarios.

hep-ex↗

arXiv2006

Inclusive Hadron Production in p+p Collisions at STAR

The STAR experiment at RHIC has measured a variety of inclusive hadron cross sections in $p+p$ collisions at Sqrt(s) = 200 GeV. Measurements of the differential cross section for inclusive charged pion production at mid rapidity and for inclusive neutral pion production at forward rapidity (3.0 < eta < 4.2) as well as the first preliminary result from STAR for the differential cross section for inclusive neutral pion production near mid rapidity are presented. These cross sections are compared to next-to-leading order perturbative QCD calculations and can provide constraints on the pion fragmentation functions. Good agreement between data and pQCD has been found for all three cross sections.

hep-ex↗

arXiv2006

An Integrated Tracker for STAR

physics.ins-det↗

arXiv2006

STAR Spin related future detector upgrades

The STAR experiment at the Relativistic Heavy Ion Collider (RHIC) has a rich spin physics program aimed at exploring the spin structure of the proton with polarized proton beams. In addition to the currently accessible channels, heavy flavor, charged vector boson production and forward mesons are integral parts of the long-term program. Such measurements require upgrades of the STAR tracking system and calorimetry. We are presenting an overview of the planned upgrades and the physics objectives driving them.

physics.ins-det↗

arXiv2006

Double Longitudinal Spin Asymmetry in Inclusive Jet Production in Polarized p+p Collisions at Sqrt(s) = 200 GeV

We present preliminary measurements of the cross section and the double longitudinal spin asymmetry in inclusive jet production in polarized p+p collisions at Sqrt(s) = 200 GeV. The measured cross section agrees well with NLO pQCD calculations over seven orders of magnitude. The observed spin asymmetries are consistent with theoretical evaluations based on deeply inelastic scattering data and tend to disfavor a large positive gluon polarization.

hep-ex↗

arXiv2006

Forward Lambda Production and Nuclear Stopping Power in d+Au Collisions at RHIC

Using the forward time projection chambers of STAR we measure the centrality dependent Lambda and Anti-Lambda yields in d+Au collisions at \sqrt{s_{NN} = 200 GeV at forward and backward rapidities. The contributions of different processes to particle production and baryon transport are probed exploiting the inherent asymmetry of the d+Au system. While the d side appears to be dominated by multiple independent nucleon-nucleon collisions, nuclear effects contribute significantly on the Au side. Using the constraint of baryon number conservation, the rapidity loss of baryons in the incoming deuteron can be estimated as a function of centrality. This is compared to a model and to similar measurements in Au+Au, which gives insights into the nuclear stopping power at relativistic energies.

nucl-ex↗

arXiv2005

Lambda Production at Forward and Backward Rapidity in d+Au Collisions at sqrt(s_NN) = 200 GeV

Using the forward time projection chambers of the STAR experiment at the Brookhaven Relativistic Heavy Ion Collider we measure the centrality dependent Lambda and Anti-Lambda yields and inverse slope parameters in d+Au collisions at forward and backward rapidities y = +- 2.75. The contributions of different processes to stopping and baryon transport are probed exploiting the inherent asymmetry of the d+Au system. Comparisons to model calculations show that the baryon transport on the deuteron side is due to multiple collisions of the deuteron nucleons with gold participants. On the gold side, the inclusion of inital state nuclear effects or hadronic rescattering is necessary to describe the data.

nucl-ex↗

arXiv2004

$Λ$ Production at High Rapidity in d+Au Collisions at $\sqrt{s_{NN}} = 200$ GeV

We present first preliminary studies of $Λ$ and $\barΛ$ production in the pseudorapidity region $2.5 < |η| < 4$, covered by the forward radial-drift TPCs (FTPCs) in STAR. The FTPCs provide momentum and charge determination but no particle identification, making the use of combinatorial methods and background subtraction necessary for $Λ$ identification. The $\barΛ/Λ$ ratio measured at high rapidity is compared to the ratio obtained at mid-rapidity with the STAR TPC. Differences in the ratio at positive and negative rapidity point to an asymmetry in particle and antiparticle production in d+Au collisions.

nucl-ex↗