118831884
Physics with a High Intensity Proton Source at Fermilab: Project X Golden Book
Within the next ten years the Standard Model will likely have to be modified to encompass a wide range of newly discovered phenomena, new elementary particles, new symmetries, and new dynamics. These phenomena will be revealed through experiment with high energy particle accelerators, mainly the LHC. This will represent a revolution in our understanding of nature, and will either bring us closer to an understanding of all phenomena, through existing ideas such as supersymmetry to superstrings, or will cause us to scramble to find new ideas and a new sense of direction. We are thus entering a dramatic and important time in the quest to understand the fundamental laws of nature and their role in shaping the universe. The energy scales now probed by the Tevatron, of order hundreds of GeV, will soon be subsumed by the LHC and extended up to a few TeV. We expect the unknown structure of the mysterious symmetry breaking of the Standard Model to be revealed. We will then learn the answer to a question that has a fundamental bearing upon our own existence: 'What is the origin of mass?' All modern theories of 'electroweak symmetry breaking' involve many new particles, mainly to providemore » a 'naturalness' rationale for the weak scale. Supersymmetry (SUSY) represents extra (fermionic) dimensions of space, leading to a doubling of the number of known elementary particles and ushering in many additional new particles and phenomena associated with the various symmetry breaking sectors. The possibility of additional bosonic dimensions of space would likewise usher in an even greater multitude of new states and new phenomena. Alternatively, any new spectroscopy may indicate new principles we have not yet anticipated, and we may see new strong forces and/or a dynamical origin of mass. The wealth of new particles, parameters, CP-phases, and other phenomena carries important implications for precision quark flavor physics experiments that are uniquely sensitive probes of new phenomena. We have already begun to see the enlargement of the Standard Model in the leptonic sector. Neutrino masses and mixing angles, which in the early 1990's were unknown, must now be incorporated into our full description of nature. In a minimal scenario of Majorana masses and mixings amongst the three known left-handed neutrinos, we see a strong hint of a new and very large mass scale, possibly associated with grand unification or the scale of quantum gravity, the Planck mass. We are not yet sure what the proper description of neutrino masses and mixing angles will be. Experiments may reveal additional unexpected particles coupled to the neutrino sector. New phenomena, such as leptonic CP-violation, will be major focal points of our expanding understanding of the lepton sector. There is much to be done with experiment to attack the issues that neutrinos now present. Already, developments in neutrino physics and the possibility of a novel source of CP-violation in the lepton sector have spawned hopes that the cosmic matter-antimatter asymmetry may be explained through leptogenesis. Neutrino physics, together with the search for new energy frontier physics, offers the possibility of experimental handles on the questions of dark matter and dark energy. Without the discovery of new particles in accelerator experiments, the telescope-based cosmological observations of the early universe would remain unexplained puzzles. The process of understanding the laws of physics in greater detail through accelerator-based high energy physics will potentially have incisive impact on our understanding of dark matter and dark energy. Precision flavor physics in both the quark and the lepton sectors offers a window on the sensitive entanglement of beyond-the-Standard-Model physics with rare processes, through quantum loop effects involving known or new states. Flavor physics offers sensitive indirect probes and may be the first place to reveal additional key components of the post-Standard Model physics. The main arenas for quark flavor physics include strange, charm and beauty, hence kaons, D-mesons, B-mesons and heavy baryons. A remarkable historical paradigm for the importance of flavor physics is the well known suppression of flavor-changing neutral currents. The analysis of the K{sub L}-K{sub S} mass difference by Gaillard and Lee, 35 years ago in the Fermilab Theory Group, led to the confirmation of the GIM mechanism and predicted the mass of the charm quark, m{sub c} {approx} 1.5 GeV, definitively and prior to its discovery. This, today, implies an astonishing constraint on SUSY models, e.g., that the down and strange squarks are mass degenerate to 1:10{sup 5}. This, in turn, has spawned a new working hypothesis called 'Minimal Flavor Violation' (MFV). But is MFV really a true principle operating in nature and, if so, where does it come from? Such questions can only be addressed in precision flavor physics experiments.« less
122778003
Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV
A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20 to 350 GeV and beam impact points and angles corresponding to pseudorapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit.
18311078
Design and prototype tests of the RPC system for the OPERA spectrometers
The Inner Tracker system of the spectrometers of the OPERA experiment makes use of Resistive Plate Chambers (RPC) in a large-scale application. We present here the definition of the project and the full design of the Inner Tracker. Specific performances for the OPERA-RPC in the spectrometer are also reported. Particle detection, muon identification and trigger capability are discussed, in particular. Some results from test beam (T9 and T7 lines at the CERN PS) and measurements from laboratory test (CERN, Frascati, Padova, Gran Sasso) with prototype detectors are discussed, as well as specific solutions developed for the final set-up in OPERA. Full Monte Carlo simulations of the experimental set-up have been also developed. r 2003 Published by Elsevier Science B.V.
183101397
PRECISION MEASUREMENTS FROM THE NOMAD EXPERIMENT
59366071
Determination of Strange Sea Quark Distributions from Fixed-target and Collider Data
We present an improved determination of the strange sea distribution in the nucleon with constraints coming from the recent charm production data in neutrino-nucleon deep-inelastic scattering by the NOMAD and CHORUS experiments and from charged current inclusive deep-inelastic scattering at HERA. We demonstrate that the results are consistent with the data from the ATLAS and the CMS experiments on the associated production of W ± -bosons with c-quarks. We also discuss issues related to the recent strange sea determination by the ATLAS experiment using LHC collider data.
110065803
Status of design and construction of the Transition Radiation Tracker (TRT) for the ATLAS experiment at the LHC
The ATLAS Inner Detector consists of three sub-systems, the Pixel Detector at the innermost radius, the Semi-Conductor Tracker at intermediate radii, and the Transition Radiation Tracker (TRT) at the outermost radius in front of the electromagnetic calorimeter. The TRT provides a combination of continuous tracking with many projective measurements based on individual drift-tubes (or straws) and of electron identification based on radiator fibres or foils interleaved between the straws themselves. This paper describes the current status of design and construction of the various components of the TRT: the assembly of the barrel modules has recently been completed, that of the end-cap wheels is well underway, and the on-detector front-end electronics is in production. The detector modules and front-end electronics boards will be integrated together over the next year, the barrel and end-cap TRT parts will be assembled and tested with their SCT counterparts during 2005 and installation and commissioning in the ATLAS pit will take place at the end of 2005 and the beginning of 2006. (C) 2004 Elsevier B.V. All rights reserved. (Less)
118897253
Translational Spacetime Symmetries in Gravitational Theories
How to include spacetime translations in fibre bundle gauge theories has been a subject of controversy, because spacetime symmetries are not internal symmetries of the bundle structure group. The standard method for including affine symmetry in differential geometry is to define a Cartan connection on an affine bundle over spacetime. This is equivalent to (1) defining an affine connection on the affine bundle, (2) defining a zero section on the associated affine vector bundle and (3) using the affine connection and the zero section to define an 'associated solder form', whose lift to a tensorial form on the frame bundle becomes the solder form. The zero section reduces the affine bundle to a linear bundle and splits the affine connection into translational and homogeneous parts; however, it violates translational equivariance/gauge symmetry. This is the natural geometric framework for Einstein–Cartan theory as an affine theory of gravitation. The last section discusses some alternative approaches that claim to preserve translational gauge symmetry.
116902880
Low Momentum Direct Photons as a Probe of Heavy Ion Collisions
of the Dissertation Low Momentum Direct Photons as a Probe of Heavy Ion Collisions
119218875
Derivation of Einstein-Cartan theory from general relativity
General relativity cannot describe exchange of orbital angular momentum and intrinsic angular momentum (spin). In 1922 E. Cartan proposed extending general relativity by including affine torsion, which resolves this problem. In 1986 the author published a derivation of Einstein-Cartan theory from general relativity with classical spin, with no additional assumptions. This paper adds simpler explanations, more computational details of the proof of the main result, correction of a factor of 2, a summary of the evidence in support of Einstein-Cartan theory, and a discussion of comments about the derivation.
59439853
Centrality categorization for Rp(d)+A in high-energy collisions
High-energy proton- and deuteron-nucleus collisions provide an excellent tool for studying a wide array of physics effects, including modifications of parton distribution functions in nuclei, gluon saturation, and color neutralization and hadronization in a nuclear environment, among others. All of these effects are expected to have a significant dependence on the size of the nuclear target and the impact parameter of the collision, also known as the collision centrality. In this article, we detail a method for determining centrality classes in p(d) + A collisions via cuts on the multiplicity at backward rapidity (i.e., the nucleus-going direction) and for determining systematic uncertainties in this procedure. For d + Au collisions at root s(NN) = 200 GeV we find that the connection to geometry is confirmed by measuring the fraction of events in which a neutron from the deuteron does not interact with the nucleus. As an application, we consider the nuclear modification factors Rp(d)+A, for which there is a bias in the measured centrality-dependent yields owing to auto correlations between the process of interest and the backward-rapidity multiplicity. We determine the bias-correction factors within this framework. This method is further tested using the HIJING Monte Carlo generator. We find that for d + Au collisions at root s(NN) = 200 GeV, these bias corrections are small and vary by less than 5% (10%) up to p(T) = 10 (20) GeV/c. In contrast, for p + Pb collisions at v root s(NN) = 5.02 TeV we find that these bias factors are an order of magnitude larger and strongly pT dependent, likely attributable to the larger effect of multiparton interactions.
117347696
sPHENIX: An Upgrade Concept from the PHENIX Collaboration
The PHENIX collaboration presents a concept for a major upgrade to the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). This upgrade, referred to as sPHENIX, brings exciting new capability to the RHIC program by opening new and important channels for experimental investigation and utilizing fully the luminosity of the recently upgraded RHIC facility. sPHENIX enables a compelling jet physics program that will address fundamental questions about the nature of the strongly coupled quark-gluon plasma discovered experimentally at RHIC to be a perfect fluid. The upgrade concept addresses specific questions whose answers are necessary to advance our understanding of the quark-gluon plasma: (1) How to reconcile the observed strongly coupled quark-gluon plasma with the asymptotically free theory of quarks and gluons? (2) What are the dynamical changes to the quark-gluon plasma in terms of quasiparticles and excitations as a function of temperature? (3) How sharp is the transition of the quark-gluon plasma from the most strongly coupled regime near Tc to a weakly coupled system of partons known to emerge at asymptotically high temperatures? In three Appendices, we detail the additional physics capabilities gained through further upgrades: (A) two midrapidity detector additions, (B) a forward rapidity upgrade, and (C) an evolution to an ePHENIX detector suitable for a future Electron Ion Collider at RHIC.