122225376
An investigation of the antinuclei and nuclei production mechanism in Pb + Pb collisions at 158 A GeV
We investigate the production mechanisms of p, d, t, 3He, 4He, 6Li, , and in Pb+Pb collisions at 158 A GeV measured near zero transverse momentum with the NA52 experiment at the CERN SPS. We find evidence that nuclei and antinuclei in Pb+Pb collisions are mainly produced via the coalescence mechanism out of a thermalized source of hadrons, at a time close to the thermal freeze-out of hadrons corresponding to a temperature of ~120 MeV.
123035541
The NA52 strangelet search
The NA52 experiment searches for long-lived charged strangelets in 158 A GeV c-1 Pb + Pb collisions at CERN SPS. The experiment is able to identify single particles coming from the collisions at pt = 0. We collected 1013 Pb + Pb interactions looking for negatively charged strangelets and 3 × 1011 Pb + Pb interactions for positively charged ones. No evidence for the production of strangelets has been observed. We present here resulting experimental differential and total upper production limits.
110306203
SVX4 User's manual
We present and describe the operation of the SVX4 chip. The SVX4 is a custom 128-channel analog to digital converter chip used by D0 and CDF in Run IIb to read out their respective silicon strip detectors. Each channel consists of an integrator (Front-End device, or FE) and a digitize/readout section (Back-End device, or BE). The input to each channel is sampled and temporarily stored in its own storage capacitor. Upon receiving a trigger signal, the relevant pipeline cell is reserved. Subsequent signals cause reserved cells to be digitized by a 128 parallel channel Wilkinson type 8-bit ADC, and then readout in byte-serial mode with optional zero suppression (sparsification). Salient features include (1) operation in either D0 mode or CDF mode (CDF mode features ''dead timeless operation'' or continued acquisition during digitization and readout) with an additional mixed mode of operation, (2) adjustable, loadable control parameters, including the integrator bandwidth and ADC polarity (only one input charge polarity will be used for Run IIb, but this feature remains for diagnostic purposes), (3) sparsified readout with nearest neighbor logic, (4) built-in charge injection with the ability for external voltage overriding for testing and calibration, and (5) a channel mask that ismore » used for either charge injection or for masking of channels with excessive DC current input during chip operation. This document is meant to familiarize the user with the functionality of the SVX4 and goes on to include specifications, pin outs, timings and electrical information. Additional information on the SVX4 can be found in Ref [1].« less
124388402
Strangelet search and particle production studies in Pb + Pb collisions at 158-A-GeV/c at CERN SPS
We searched for long-lived strange quark matter particles, so-calledstrangelets, and studied particle and antiparticle production in Pb+Pb collisions at 158 GeV/c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/c 2 and lifetimest lab>1.2 μs and plot invariant differential production cross sections as a function of rapidity for a variety of particles.
118548096
Measurement of the two-photon absorption cross-section of liquid argon with a time projection chamber
This paper reports on laser-induced multiphoton ionization at 266?nm of liquid argon in a time projection chamber (LAr TPC) detector. The electron signal produced by the laser beam is a formidable tool for the calibration and monitoring of next-generation large-mass LAr TPCs. The detector that we designed and tested allowed us to measure the two-photon absorption cross-section of LAr with unprecedented accuracy and precision: ?ex=(1.24?0.10stat?0.30syst)?10? 56?cm4?s? 1.
117231264
Development of readout system for double-sided silicon strip modules
Y. Takubo ∗,a S. Gonzalez-Sevilla, c A. Clark, c M. Endo, b D. Ferrere, c K. Hanagaki, b Y. Ikegami, a S. Terada,a Y. Unno a and M. Weber c a High Energy Accelerator Research Organization (KEK) 1-1 Oho, Tsukuba, Ibaragi, Japan b Department of Physics, Osaka University 1-1 Machikaneyama Toyonaka Osaka, Japan c DPNC, University of Geneva 24, quai Ernest-Ansermet CH-1211 Geneva 4, Switzerland E-mail: yosuke.takubo@kek.jp
17193732
JET PRODUCTION AT HERA : PROGRESS AND PROBLEMS
This contribution reviews the measurements related to jet production at HERA which are available in`98. The reasons for the considerable progress achieved in the last years are summarized. The major diiculties and the limitations of these measurements as seen today are discussed. 1. What has been measured ? One of the many fascinating topics of research at the electron{proton collider HERA is the study of multi{jet events. The application of jet algorithms to characterize the properties of multi{particle hadronic nal states turned out to be a powerful and natural approach. Jet algorithms have been used intensively in the analysis of deeply inelastic scattering (DIS) and photoproduction processes. In leading{order QCD, the cross section of multi{jet events in DIS is proportional to the strong coupling constant s and the parton density functions of the proton. Several determinations of s based on jets have been performed at HERA 1, 2, 3, 4]. There are (preliminary) extractions of the proton's gluon content in NLO 5]. This approach is more direct than determinations of the gluon density from inclusive structure function measurements, and it probes the gluon density at larger momentum fractions. Events with a jet in the very forward (proton) direction of the detectors have been studied in attempts to search for signatures expected when the BFKL parton density evolution equations are valid at HERA 6]. In photoproduction, evidence for the partonic structure of the photon has been shown in studies of jet distributions 7]. In events with two reconstructed jets x , the share of the photon's momentum entering the hard scattering process, can be calculated. From the measurement of dijet cross sections diierential in x and transverse jet energy, photon parton densities could be constrained, and the p t dependence of the anomalous component of the real photon predicted by QCD could be connrmed 8]. Jet polar angle distributions for direct and resolved photons where measured to be sensitive to the spin of the corresponding gluon or quark propagators 9]. Also, LO eeective parton densities were extracted 8].
119389130
Electroweak corrections to e+ e- -> nu anti-nu H and e+ e- -> t anti-t H
The most interesting Higgs-production processes at future e+ e- colliders belong to the process class e+ e- ->f anti-f H. We study the full O(alpha) corrections to this reaction in the Standard Model for neutrinos and top quarks in the final state. Leading higher-order corrections from initial-state radiation and QCD corrections are also taken into account. Although cancellations between the different kinds of corrections occur, the full corrections are of the order of +/-10% and thus important ingredients in the theoretical predictions for future e+ e- colliders.
53579185
Higgs production and decay with a fourth Standard-Model-like fermion generation
State-of-the-art predictions for the Higgs-boson production cross section via gluon fusion and for all relevant Higgs-boson decay channels are presented in the presence of a fourth Standard-Model-like fermion generation. The qualitative features of the most important differences to the genuine Standard Model are pointed out, and the use of the available tools for the predictions is described. For a generic mass scale of 400−600 GeV in the fourth generation explicit numerical results for the cross section and decay widths are presented, revealing extremely large electroweak radiative corrections, e.g., to the cross section and the Higgs decay into WW or ZZ pairs, where they amount to about −50 % or more. This signals the onset of a non-perturbative regime due to the large Yukawa couplings in the fourth generation. An estimate of the respective large theoretical uncertainties is presented as well.
116194687
Scintillator materials for calorimetry
Requirements for fast, dense scintillator materials for calorimetry in high energy physics and approaches to satisfying these requirements are reviewed with respect to possible hosts and luminescent species. Special attention is given to cerium-activated crystals, core-valence luminescence, and glass scintillators. The present state of the art, limitations, and suggestions for possible new scintillator materials are presented.