120275712
Evolution of silicon microstrip detector currents during proton irradiation at the CERN PS
Prototype ATLAS silicon microstrip detectors have been irradiated to the dose predicted for 10 years of LHC operation with 24 GeV protons at the CERN PS whilst cooled to the ATLAS design operating temperature. The detector currents were monitored during irradiation, which allows the predictions of bulk radiation damage parameterizations to be tested. Values for the damage constant a and the rate of acceptor creation b have been calculated and are in agreement with those previously published for the irradiation of silicon diodes. r 2002 Elsevier Science B.V. All rights reserved. PACS: 29.40.Wk; 61.82.Fk
125401428
Measurement of the cross section of high transverse momentum $\it{Z\rightarrow b\bar{b}}$ production in proton--proton collisions at $\sqrt{s}=8 TeV$ with the ATLAS Detector
121864227
Progress with the single-sided module prototypes for the ATLAS tracker upgrade stave
Abstract The ATLAS experiment is preparing for the planned luminosity upgrade of the LHC (the super-luminous LHC or sLHC) with a programme of development for tracking able to withstand an order of greater magnitude radiation fluence and much greater hit occupancy rates than the current detector. This has led to the concept of an all-silicon tracker with an enhanced performance pixel-based inner region and short-strips for much of the higher radii. Both sub-systems employ many common technologies, including the proposed “stave” concept for integrated cooling and support. For the short-strip region, use of this integrated stave concept requires single-sided modules mounted on either side of a thin central lightweight support. Each sensor is divided into four rows of 23.82 mm length strips; within each row, there are 1280 strips of 74.5μm pitch. Well over a hundred prototype sensors are being delivered by Hamamatsu Photonics (HPK) to Japan, Europe and the US. We present results of the first 20 chip ABCN25 ASIC hybrids for these sensors, results of the first prototype 5120 strip module built with 40 ABCN25 read-out ASICs, and the status of the hybrids and modules being developed for the ATLAS tracker upgrade stave programme.
9225555
The barrel modules of the ATLAS semiconductor tracker.
This paper describes the silicon microstrip modules in the barrel section of the SemiConductor Tracker (SCT) of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The module requirements, components and assembly techniques are given, as well as first results of the module performance on the fully assembled barrels that make up the detector being installed in the ATLAS experiment.
123114924
ATLAS measurements of the properties of jets for boosted particle searches
Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of root s = 7 TeV. The data correspond to an integrated luminosity of 35 pb(-1) and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-k(t) algorithm with distance parameters R 0: 6 and 1.0, with transverse momentum p(T) > 300 GeV and pseudorapidity vertical bar eta vertical bar < 2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describe the general features of the jets, although discrepancies are observed in some distributions.
120963337
ATLAS beam test results
Abstract Many different configurations of electronics and semiconductor strip detectors were studied in 1995 using the ATLAS tracking detector test area at the H8 beam-line of the CERN SPS. A significant fraction of these investigations are presented elsewhere in this volume and this paper will concentrate on the results with silicon strip detectors read out with electronics preserving the pulse height information. Data has been collected with the ADAM, APV5 and FElix read-out chips on a number of different detectors. The first results are presented for read out with LHC electronics of detectors to the ATLAS-A specification of 112.5 μm pitch, employing n-strips in n-type silicon, capacitive coupling and intermediate strips. It is demonstrated that with adequate signal/noise, a spatial resolution of ⋍13 μm is attainable with these detectors.
118476252
More flavor SU(3) tests for new physics in CP violating B decays
A bstractThe recent LHCb measurements of the Bs → K−π+ and Bs → K+K− rates and CP asymmetries are in agreement with U-spin expectations from Bd → K+π− and Bd → π+π− results. We derive the complete set of isospin, U-spin, and SU(3) relations among the CP asymmetries in two-body charmless B → PP and B → PV decays, some of which are novel. To go beyond the unbroken SU(3) limit, we present relations which are properly defined and normalized to allow incorporation of SU(3) breaking in the simplest manner. We show that there are no CP relations beyond first order in SU(3) and isospin breaking. We also consider the corresponding relations for charm decays. Comparing parametrizations of the leading order sum rules with data can shed light on the applicability and limitations of both the flavor symmetry and factorization-based descriptions of SU(3) breaking. Two factorization relations can already be tested, and we show they agree with current data.
118492998
SU(3) sum rules for charm decay
A bstractWe present flavor SU(3) sum rules for D → PP and D → PV decay amplitudes, that are valid to second order in symmetry breaking by the strange quark mass spurion. Decay rate sum rules are also computed to this order. Particular attention is given to sum rules arising from the isospin and U-spin subgroups, the former providing sensitive tests for alternative sources of SU(3) breaking. We apply the latter together with the postulated ΔU = 0 rule for the large penguin picture to predict the ratio and difference of the direct CP asymmetries for D → KK∗ and D → πρ.
117823450
Linear in temperature resistivity of scalar fermions: application to high Tc cuprates
no longer applicable
118549709
Galactic center gamma-ray excess through a dark shower
The reported excess of $\gamma$-rays, emitted from an extended region around the galactic center, has a distribution and rate suggestive of an origin in dark matter (DM) annihilations. The conventional annihilation channels into standard model (SM) $b$ quarks or $\tau$ leptons may, however, be in tension with various experimental constraints on antiproton and positron fluxes. We present a framework that is free from such constraints. The key idea is that the mediators between the dark matter and the SM are themselves part of a strongly coupled sector: a hidden valley. In this scenario, the dark matter particles annihilate only into hidden quarks that subsequently shower and hadronize. Hidden quark effective couplings to SM hypercharge allow the lightest hidden bound states to subsequently decay into SM photons, producing the observed photon energy spectrum. Associated production of SM fermions is, in contrast, suppressed by electroweak, loop or helicity effects. We find that, generically, $\sim$ 10 GeV DM and a confinement scale $\sim$ 1 GeV provide a good fit to the observed spectrum. An $SU(2)$ hidden confining group is preferred over $SU(3)$ or higher rank gauge groups, up to uncertainties in the extraction of the astrophysical background. An explicit realization of this framework is also presented, and its phenomenology is discussed in detail, along with pertinent cosmological, astrophysical and collider bounds. This framework may be probed by model-independent searches, including future beam-dump experiments.
119261475
Composite Dirac neutrinos
We present a mechanism that naturally produces light Dirac neutrinos. The basic idea is that the right-handed neutrinos are composite. Any realistic composite model must involve ‘hidden flavor’ chiral symmetries. In general some of these symmetries may survive confinement, and in particular, one of them manifests itself at low energy as an exact B − L symmetry. Dirac neutrinos are therefore produced. The neutrinos are naturally light due to compositeness. In general, sterile states are present in the model, some of them can naturally be warm dark matter candidates.