117006835
Future Possibilities for Lepton-Hadron Collider Physics and Detectors
We have considered the physics opportunities of future lepton-hadron colliders and how these opportunities might be realized in a possible polarized eRHIC facility and an e-p collider as part of a staged or final version VLHC. We evaluated the physics priorities based on experience at HERA and, using simulated data for e-p collisions with √ s > 1 TeV, showed how detector designs would be
106619805
LC HCAL Absorber And Active Media Comparisons Using a Particle-Flow Algorithm
We compared Stainless Steel (SS) to Tungsten (W) as absorber for the HCAL in simulation using single particles (pions) and a Particle-Flow Algorithm applied to e{sup +}e{sup -} -> Z -> qqbar events. We then used the PFA to evaluate the performance characteristics of a LC HCAL using W absorber and comparing scintillator and RPC as active media. The W/Scintillator HCAL performs better than the SS/Scintillator version due to finer {lambda}{sub I} sampling and narrower showers in the dense absorber. The W/Scintillator HCAL performs better than the W/RPC HCAL except in the number of unused hits in the PFA. Since this represents the confusion term in the PFA response, additional tuning and optimization of a W/RPC HCAL might significantly improve this HCAL configuration.
26693719
Measurement of charged and neutral current e-p deep inelastic scattering cross sections at high Q2.
Deep inelastic e-p scattering has been studied in both the charged current (CC) and neutral current (NC) reactions at momentum transfers squared Q 2 above 400 GeV 2 using the ZEUS detector at the HERA ep collider. The CC and NC total cross sections, the NC to CC cross section ratio, and the differential cross sections dσ/dQ 2 are presented. From the Q 2 dependence of the CC cross section, the mass term in the CC propagator is determined to be M W = 76±16±13 GeV.
112157717
Use of Particle Flow Algorithms in a Dual Readout Crystal Calorimeter
The ability to grow clear, dense scintillating crystals presents an opportunity for development of a total absorption calorimeter that could contain multi-GeV hadrons in a detector volume similar to that of present-day calorimeters. With appropriate crystals and optimized readout elements, both scintillation and Cerenkov photons can be produced and detected separately. This dual readout approach allows one to selectively correct particle energies, resulting in significant gains in energy resolution →20%/√E or even better for hadrons. An R&D program is underway to 1) develop appropriate clear, dense crystals, 2) test innovative readout methods for both scintillation and Cerenkov light, and 3) provide test beam capability for crystal and readout sensor testing and simulation verification. As part of this effort, simulation studies have been done assuming a dual readout crystal calorimeter implementation for a future e+e− linear collider detector. By using the dual readout correction, corrections for magnetic field effects on low momentum charged hadrons, and particle flow techniques, substantial improvements in dijet mass resolution are obtained.
121348800
ZEUS results from the first year: DIS cross section and hadronic final states
The first year of operation of the HERA electron-proton collider has resulted in deep inelastic scattering (DIS) physics results from both the H1 and ZEUS experiments. Reported are results from the ZEUS collaboration on the measurement of the DIS neutral-current cross section, which has been made at higher Q2 and lower xBj than previously reported from fixed-target experiments. The final-state hadronic energy flow has been studied, and comparison with various QCD Monte Carlo model shows that QCD radiation has a strong influence on its characteristics. The observation of multi-jet production in DIS neutral-current events is also reported.
118751100
The TrICE prototype MAMPT imaging camera
The Track Imaging Cerenov Experiment (TrICE) is an air Cerenkov prototype telescope designed to use multi-anode photomultiplier to acheive a high angular resolution for measuring cosmic-ray composition at TeV-PeV energies. The TrICE camera, composed of 16 Hamamatsu R8900 16-channel multi-anode photomultiplier tubes, achieves 0.086 degree angular width per pixel over 1.5 degree wide field of view. We present a description of the TrICE camera design, calibration and performance.
40017204
WASP-41b: A Transiting Hot Jupiter Planet Orbiting a Magnetically Active G8V Star
ABSTRACT.We report the discovery of a transiting planet with an orbital period of 3.05 days orbiting the star TYC 7247-587-1. The star, WASP-41, is a moderately bright G8 VV star (V = 11.6V=11.6) with a metallicity close to solar ([Fe/H] = -0.08 ± 0.09[Fe/H]=-0.08±0.09). The star shows evidence of moderate chromospheric activity, both from emission in the cores of the Ca ii H and K ines and photometric variability with a period of 18.4 days and an amplitude of about 1%. We use a new method to show quantitatively that this periodic signal has a low false-alarm probability. The rotation period of the star implies a gyrochronological age for WASP-41 of 1.8 Gyr with an error of about 15%. We have used a combined analysis of the available photometric and spectroscopic data to derive the mass and radius of the planet (0.92 ± 0.06 MJup0.92±0.06  MJup, 1.20 ± 0.06 RJup1.20±0.06  RJup). Further observations of WASP-41 can be used to explore the connections between the properties of hot Jupiter planets and the leve...
16811346
Temperature and cooling age of the white dwarf companion of PSR J0218+4232
We report on Keck optical BVRI images and spectroscopy of the companion of the binary millisecond pulsar PSR J0218+4232. A faint bluish (V = 24.2, B - V = 0.25) counterpart is observed at the pulsar location. Spectra of this counterpart reveal Balmer lines which confirm that the companion is a helium-core white dwarf. We find that the white dwarf has a temperature of T_(eff) = 8060 ± 150 K. Unfortunately, the spectra are of insufficient quality to put a strong constraint on the surface gravity, although the best fit is for low log g and hence low mass (~0.2 M_⊙), as expected. We compare predicted white dwarf cooling ages with the characteristic age of the pulsar and find similar values for white dwarf masses of 0.19 to 0.3 M_⊙. These masses would imply a distance of 2.5 to 4 kpc to the system. The spectroscopic observations also enable us to estimate the mass ratio between the white dwarf and the pulsar. We find q = 7.5 ± 2.4, which is consistent with the current knowledge of white dwarf companions to millisecond pulsars.
18942639
Femtoscopically Probing the Freeze-out Configuration in Heavy Ion Collisions
Two-particle femtoscopy reveals the space-time substructure of the freeze-out configuration from heavy ion collisions. Detailed fingerprints of bulk collectivity are evident in space-momentum correlations, which have been systematically measured as a function of particle type, three-momentum, and collision conditions. A clear scenario, dominated by hydrodynamic-type flow emerges. Reproducing the strength and features of the femtoscopic signals in models involves important physical quantities like the Equation of State, as well as less fundamental technical details. An interesting approximate "factorization" in the measured systematics suggests that the overall physical freeze-out scale is set by final state chemistry, but the kinematic substructure is largely universal. Referring to previous results from hadron and lepton collisions, we point to the importance of determining whether these "universal" trends persist from the largest to the smallest systems. We review theoretical expectations for heavy ion femtoscopy at the LHC, and point to directions needing further theory and experimental work at RHIC and the LHC.
7071388
Nonperturbative versus perturbative effects in generalized parton distributions
Generalized parton distributions (GPDs) are studied at the hadronic (nonperturbative) scale within different assumptions based on a relativistic constituent quark model. In particular, by means of a meson-cloud model we investigate the role of nonperturbative antiquark degrees of freedom and the valence-quark contribution. A QCD evolution of the obtained GPDs is used to add perturbative effects and to investigate the GPDs' sensitivity to the nonperturbative ingredients of the calculation at larger (experimental) scale.
17088589
Analytic treatment of positronium spin splittings in light-front QED
We study the QED bound-state problem in a light-front Hamiltonian approach. Starting with a bare cutoff QED Hamiltonian H{sub B} with matrix elements between free states of drastically different energies removed, we perform a similarity transformation that removes the matrix elements between free states with energy differences between the bare cutoff {Lambda} and effective cutoff {lambda} ({lambda}{lt}{Lambda}). This generates effective interactions in the renormalized Hamiltonian H{sub R}. These effective interactions are derived to order {alpha} in this work, with {alpha}{lt}1. H{sub R} is renormalized by requiring it to satisfy coupling coherence. A nonrelativistic limit of the theory is taken, and the resulting Hamiltonian is studied using bound-state perturbation theory. The effective cutoff {lambda}{sup 2} is fixed, and the limit 0{l_arrow}m{sup 2}{alpha}{sup 2}{lt}{lambda}{sup 2}{lt}m{sup 2}{alpha}{r_arrow}{infinity} is taken. This upper bound on {lambda}{sup 2} places the effects of low-energy (energy transfer below {lambda}) emission in the effective interactions in the {vert_bar}e{bar e}{r_angle} sector. This lower bound on {lambda}{sup 2} ensures that the nonperturbative scale of interest is not removed by the similarity transformation. As an explicit example of the general formalism introduced, we show that the Hamiltonian renormalized to O({alpha}) reproduces the exact spectrum of spin splittings, with degeneracies dictated by rotationalmore » symmetry, for the ground state through O({alpha}{sup 4}). The entire calculation is performed analytically, and gives the well-known singlet-triplet ground-state spin splitting of positronium, (7)/(6){alpha}{sup 2}Ryd. We discuss the remaining corrections other than the spin splittings and how they can be treated in calculating the spectrum with higher precision. {copyright} {ital 1997} {ital The American Physical Society}« less