53402380
Monte Carlo tools for studies of non-standard electroweak gauge boson interactions in multi-boson processes: A Snowmass White Paper
In this Snowmass 2013 white paper, we review the effective field theory approach for studies of non-standard electroweak interactions in electroweak vector boson pair and triple production and vector boson scattering. We present an overview of the implementation of dimension six and eight operators in MadGraph5, VBFNLO, and WHIZARD, and provide relations between the coefficients of these higher dimensions operators used in these programs and in the anomalous couplings approach. We perform a tuned comparison of predictions for multi-boson processes including non-standard electroweak interactions with MadGraph5, VBFNLO, and WHIZARD. We discuss the role of higher-order corrections in these predictions using VBFNLO and a POWHEG BOX implementation of higher-order QCD corrections to WWjj production. The purpose of this white paper is to collect useful tools for the study of non-standard EW physics at the LHC, compare them, and study the main physics issues in the relevant processes.
119257516
Di-boson and Tri-boson production at the LHC
The status of di-boson and tri-boson production is shortly review. Using the VBFNLO and the LOOPSIM package, approximated results at NNLO QCD are given for WZ production. Results for waa + jet at NLO QCD are also shown.
116260923
NLO QCD corrections to $W^\pm Z\gamma$ production with leptonic decays
We present a computation of the O(alpha_s) QCD corrections to W^\pm Z \gamma production at the Large Hadron Collider. The photon is considered as real, and we include full leptonic decays for the W and Z bosons. Based on the structure of the VBFNLO program package, we obtain numerical results through a fully flexible Monte Carlo program, which allows to implement general cuts and distributions of the final-state particles. The NLO QCD corrections are sizable and strongly exceed the theory error obtained by a scale variation of the leading-order result. Also, the shapes of relevant observables are significantly altered.
119114605
Physics beyond the standard model: supersymmetry
This collection of studies on new physics at the LHC constitutes the report of the supersymmetry working group at the Workshop 'Physics at TeV Colliders', Les Houches, France, 2007. They cover the wide spectrum of phenomenology in the LHC era, from alternative models and signatures to the extraction of relevant observables, the study of the MSSM parameter space and finally to the interplay of LHC observations with additional data expected on a similar time scale. The special feature of this collection is that while not each of the studies is explicitly performed together by theoretical and experimental LHC physicists, all of them were inspired by and discussed in this particular environment.
123906099
Helmholtz Alliance Linear Collider Forum
Supersymmetric scenarios with a very weakly interacting lightest superpartner (LSP) - like the gravitino or axino - naturally give rise to a long-lived next-to-LSP (NLSP). If the NLSP is a charged slepton it leaves a very distinct signature in a collider experiment. At the ILC/CLIC it will be possible to capture a significant fraction of the produced charged sleptons and observe their decays. These decays potentially reveal the nature of the LSP and thus provide a unique possibility to measure the properties of a very weakly interacting LSP which otherwise is most likely hidden from any other observation, like direct or indirect dark matter searches. We review the proposals that have been made to measure the LSP properties at the ILC/CLIC and compare its potential to the capability of the LHC.
246159
Complete one-loop calculation of the T-violating D-parameter in neutron decay in the MSSM
Abstract.We investigate the violation of time reversal invariance in the decay of the free neutron in the framework of the minimal supersymmetric standard model (MSSM). The coefficient of the triple product of the neutron spin and the momenta of electron and neutrino, the so-called D parameter, is computed at one-loop order including all diagrams. We find that D is mainly sensitive to the trilinear A coupling in the squark sector and to the phase of the coefficient $\mu$ which mixes the two Higgs superfields. The maximal MSSM contribution using parameters still allowed by experiment is however at $D \approx 10^{-7}$, while QED final state interactions give a value of $D_{\mathrm {fsi}} = - 2.3 \cdot 10^{-5}$. Explicit expressions for all relevant diagrams are given in an appendix.
118595197
Faint Resonantly Scattered Lyman Alpha Emission from the Absorption Troughs of Damped Lyman Alpha Systems at z ~ 3
We demonstrate that the Lyman alpha emission in the absorption troughs of a large sample of stacked damped Lyman alpha absorption systems (DLAS) presented by Rahmani et al (2010) is consistent with the spectral profiles and luminosities of a recently detected population of faint Lyman alpha emitters at z ~ 3. This result supports the suggestion that the faint emitters are to be identified with the host galaxies of DLAS at these redshifts.
1772447
An HST Study of the Supernovae Accompanying GRB 040924 and GRB 041006
The authors are grateful for support under the Space Telescope 
Science Institute grant HST-GO-10135. A. M. S. acknowledges 
support by the NASA Graduate Student Researchers Program. 
E. B. is supported by NASA through Hubble Fellowship grant 
HST-HF-01171.01 awarded by the STScI, which is operated by 
the Association of Universities for Research in Astronomy, Inc., 
for NASA, under contract NAS 5-26555. A. G. acknowledges 
support by NASA through Hubble Fellowship grant HST-HF- 
01158.01-A awarded by STScI. K. R. is supported by the Gemini 
Observatory, which provided observations presented in this paper, 
and which is operated by the Association of Universities 
for Research in Astronomy, Inc., under a cooperative agreement 
with the NSF on behalf of the Gemini partnership: the National 
Science Foundation (United States), the Particle Physics and 
Astronomy Research Council (United Kingdom), the National 
Research Council (Canada), CONICYT (Chile), the Australian 
Research Council (Australia), CNPq (Brazil), and CONICET 
(Argentina).
118217379
Small Scale Structure in the Universe and the Distribution of Baryons at High Redshift
We briefly discuss the relevance of Lyman alpha forest observations for measuring cosmological parameters, comparing the properties of high z QSO spectra with those of artifical spectra from hydrodynamic simulations, based on hierarchical cosmologies. In particular, we describe a measurement of the baryon content of the universe obtained by matching the average opacity of the Lyman alpha forest from simulations to the observed one from a new dataset observed with the Keck telescope. We then report on a search for possible small scale structure in the intergalactic medium which could be unresolved by current cosmological simulations. Observing column density gradients in the spectra of lensed QSOs we find the typical intergalactic gas cloud to be structureless down to at least the 4 % level, on scales of 0.1 kpc. Extending the study of lensed absorption to higher column densities we begin to sample the velocity field internal to high redshift galaxies. Remarkable differences in column density (of order 50 %) and projected velocity (tens of km/s) between lines of sight separated by only a few hundred parsecs are found, and we may be observing structure in the early interstellar medium.
4513101
New Statistical Measures of the Lya Forest Spectra for Accurate Comparison to Theoretical Models
We propose a new method of analysis for the \lya forest, namely to measure the 1-point and 2-point joint probability distribution of the transmitted flux. The results for a sample of seven observed quasars and from two simulations of structure formation are shown and compared. Statistically significant differences in the 2-point function between the results of the numerical simulations and the observations are easily found. The analysis we suggest is very simple to apply to observed data sets, and we discuss its superiority over the traditional Voigt-profile fitting algorithms for accurate comparison to the predictions of theoretical models.
119354809
Small-Scale Structure at High Redshift. II. Physical Properties of the C IV Absorbing Clouds
Keck HIRES spectra with a resolution of 6.6 or 4.3 km s-1 were obtained of the separate images of three gravitationally lensed QSOs, namely, Q0142-0959 A,B (UM 673 A,B; zem = 2.72), HE 1104-1805 A,B (zem = 2.32), and Q1422+231 A,C (zem = 3.62). The typical separation of the images on the sky is ~1''. The corresponding transverse distances between the lines of sight range from a few tens of kiloparsecs at the redshift of the lens to a few parsecs at the source. We studied the velocity differences and column density differences in C IV doublets in each QSO, including single isolated doublets, complex clumps of doublets, and subclumps. Unlike the low-ionization gas clouds typical of the interstellar gas in the Galaxy or damped Lyα galaxies, the spatial density distribution of C IV absorbing gas clouds turns out to be mostly featureless on scales up to a few hundred parsecs, with column density differences rising to 50% or more over separations beyond a few kiloparsecs. Similarly, velocity shear becomes detectable only over distances larger than a few hundred parsecs, rising to ~70 km s-1 at a few kiloparsecs. The absorption systems become more coherent with decreasing redshift distance to the background QSO; this finding confirms that all three QSOs used are indeed lensed, as opposed to being genuine QSO pairs. The amount of turbulence in C IV gas along and across each line of sight was measured and a crude estimate of the energy input rate obtained. The energy transmitted to the gas is substantially less than in present-day star-forming regions, and the gas is less turbulent on a given spatial scale than, e.g., local H II regions. The quiescence of C IV clouds, taken with their probable low density, implies that these objects are not internal to galaxies. The C IV absorbers could be gas expelled recently to large radii and raining back onto its parent galaxy, or pre-enriched gas from an earlier (Population III?) episode of star formation, falling into the nearest mass concentration. However, while the metals in the gas may have been formed at higher redshifts (z > 5?), the residual turbulence in the clouds and the minimum coherence length measured here imply that the gas was stirred more recently, possibly by star formation events recurring on a timescale on the order of 107-108 yr.