15696182
Precision calculations for H -> WW/ZZ -> 4fermions with PROPHECY4f
PROPHECY4f is a Monte Carlo event generator for precise simulations of the Higgs-boson decay H -> WW/ZZ -> 4fermions, supporting leptonic, semileptonic, and four-quark final states. Both electroweak and QCD corrections are included. Treating the intermediate gauge bosons as resonances, the calculation covers the full Higgs-boson mass range above, near, and below the gauge-boson pair thresholds. In this article we pay particular attention to the recently implemented option of PROPHECY4f to generate unweighted events.
119932741
Electroweak radiative corrections to e+ e- -> t anti-t H
We have calculated the complete electroweak O(alpha) radiative corrections to the Higgs-boson production process e+ e- -> t anti-t H in the electroweak Standard Model. Initial-state radiation beyond O(alpha) is included in the structure-function approach. The calculation of the corrections is briefly described, and numerical results are presented for the total cross section. Both the photonic and the genuine weak corrections reach the order of about 10% or even more and show a non-trivial dependence on the Higgs-boson mass and on the scattering energy. We compare our results with two previous calculations that obtained differing results at high energies.
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.
118320839
Gluon-Induced Weak Boson Fusion
The gluon-gluon induced terms for Higgs production through weak boson fusion (WBF) are computed. Formally, these are of next-to-next-to-leading order in the strong coupling constant. This is the lowest order at which nonzero color exchange occurs between the scattering quarks, leading to a color field and thus additional hadronic activity between the outgoing jets. Using a minimal set of cuts, the numerical impact of these terms is at the percent level with respect to the next-to-leading order rate for weak boson fusion. Applying the so-called WBF cuts leads to an even stronger suppression, so that we do not expect a significant deterioration of the WBF signal by these color exchange effects.
10525627
Electroweak radiative corrections to single Higgs-boson production in e+e− annihilation
Abstract We have calculated the complete electroweak O (α) radiative corrections to the single Higgs-boson production processes e + e − →ν l ν l H ( l =e, μ , τ ) in the electroweak Standard Model. Initial-state radiation beyond O (α) is included in the structure-function approach. The calculation of the corrections is briefly described, and numerical results are presented for the total cross-section. In the G μ scheme, the bulk of the corrections is due to initial-state radiation, which affects the cross-section at the level of −7% at high energies and even more in the ZH threshold region. The remaining bosonic and fermionic corrections are at the level of a few percent. The confusing situation in the literature regarding differing results for the fermionic corrections to this process is clarified.
16334731
Higgs Production by Gluon initiated Weak Boson Fusion
The gluon-gluon induced terms for Higgs production through weak-boson fusion are calculated. They form a finite and gauge-invariant subset of the NNLO corrections in the strong coupling constant. This is also the lowest order with sizeable t-channel colour exchange contributions, leading to additional hadronic activity between the outgoing jets.
121724105
Serial Power Protection for ATLAS Silicon Strip Staves
Abstract Upgrades to the inner tracking detectors at the Super Large Hadron Collider (SLHC) will require more efficient methods of power delivery. Serial power is one architecture that delivers power efficiently by powering a chain of front-end circuits (hybrids) with a common current. A major concern with serial power is the loss of the full hybrid chain due to an open circuit failure of a single hybrid. We propose a method to protect a serial chain of hybrids with emphasis on application to the ATLAS silicon strip upgrade. A prototype protection circuit and its discrete component implementation are described. Results from tests of the protection circuit used with individual “dummy” hybrids and in a system test with a collection of dummy hybrids are given. Finally, a path towards a radiation-hard ASIC implementation is discussed. This work demonstrates that the protection of a serial chain is viable and is not an obstacle to the implementation of serial power.
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
125660697
IS THE DARK MATTER INTERPRETATION OF THE EGRET GAMMA RAY EXCESS COMPATIBLE WITH ANTIPROTON MEASUREMENTS
16665734
Top Quark Production and Decay Properties at the Tevatron
The latest results from the CDF and D0 collaborations on the top-quark pair-production cross section and limits on electroweak production are presented. Included are measurements of properties of the top quark such as charge, lifetime, and the decay branching ratio t->Wb. In addition to measurements about the top quark, the selected event samples are used to study the helicity of the W boson and to search for additional exotic quarks (t') and resonances in the ttbar invariant mass spectrum.
14039647
JET SHAPES AND DETERMINATIONS OF s FROM HADRONIC FINAL STATES IN DEEP INELASTIC SCATTERING AT HERA
Recent results from the study of hadronic nal states in deep inelastic scattering at HERA are reviewed. Jet shapes from neutral and charged current interactions at HERA are compared to those from e + e ? annihilation and p p collisions. The (2+1) jet event rate distributions R2+1(Q 2) and y2 are measured using the modiied JADE jet algorithm. The value of the strong coupling constant s is determined from a comparison with QCD predictions in next{ to{leading order. An analysis of event shape distributions in terms of next{to{leading order QCD calculations and power corrections is presented.