118401112
W and Z bosons physics at LHC at low luminosity
The W and Z bosons production cross sections at LHC will be huge: Σ(pp → W → lv) ≈ 20 nb, Σ(pp → Z → l + l ™) ≈ 2nb. Moreover the W and Z production and decay processes have been measured with high accuracy in previous experiments. Thus the W and Z bosons will play a key role during the first data taking at LHC allowing to test the detector performances and to tune the Monte Carlo generators. In fact, with only 1fb−1 of integrated luminosity, the processes involving EW bosons will be used to calibrate Electromagnetic Calorimeters and to align Muon and Tracker Systems. With 10 fb−1 of integrated luminosity, the study of Z and W events will improve our knowledge of the Parton Distribution Functions (PDF) and it will provide a raw luminosity monitoring. In the following we will focus on these EW bosons studies achievable already at low luminosity. These analysis hold the key for all the future searches because they provide the way to control many of the main experimental and theoretical systematics at LHC.
11160721
Higgs at LHC
An overview of recent theoretical results on the Higgs boson and its discovery strategy at ATLAS and CMS will be presented, focusing on the main Higgs analysis effective with low integrated luminosity (less than 30 fb^-1).
112424559
W and Z cross sections at LHC
55754996
On the spin and parity of a single-produced resonance at the LHC
The experimental determination of the properties of the newly discovered boson at the Large Hadron Collider is currently the most crucial task in high energy physics. We show how information about the spin, parity, and, more generally, the tensor structure of the boson couplings can be obtained by studying angular and mass distributions of events in which the resonance decays to pairs of gauge bosons, $ZZ, WW$, and $\gamma \gamma$. A complete Monte Carlo simulation of the process $pp \to X \to VV \to 4f$ is performed and verified by comparing it to an analytic calculation of the decay amplitudes $X \to VV \to 4f$. Our studies account for all spin correlations and include general couplings of a spin $J=0,1,2$ resonance to Standard Model particles. We also discuss how to use angular and mass distributions of the resonance decay products for optimal background rejection. It is shown that by the end of the 8 TeV run of the LHC, it might be possible to separate extreme hypotheses of the spin and parity of the new boson with a confidence level of 99% or better for a wide range of models. We briefly discuss the feasibility of testing scenarios where the more » resonances is not a parity eigenstate. « less
59482524
Measurement of Drift Velocity in the CMS Barrel Muon Chambers at the CMS Magnet Test Cosmic Challenge
This note reports the results of the analysis performed on the data collected by the CMS Barrel Muon system during the Magnet Test-Cosmic Challenge, aimed to study the Drift Tube chambers behavior at the nominal value of the CMS magnetic field. In particular, the analysis is devoted to the study of the drift velocity in the various equipped regions of the apparatus. It is shown that the drift velocity is significantly affected by the presence of a residual magnetic field in the chamber volume only in the innermost stations, MB1, of Wheel+2; where the maximal variation inside the chamber is of 4 percent, which does not prevent a good functionality of the DT trigger even in this most critical region.
124763536
Calibration of the CMS magnetic field using cosmic muon tracks
The Compact Muon Solenoid (CMS) [1] is a general-purpose detector whose main goal is to explore physics at the TeV scale by exploiting the proton-proton collisions provided by the Large Hadron Collider (LHC) [2] at CERN. During October-November 2008, the CMS Collaboration conducted a data-taking exercise known as the Cosmic Run At Four Tesla (CRAFT) [3]: 270 million cosmic ray triggered events have been recorded with all installed detector systems participating and with the solenoid at a central magnetic flux density of 3.8 T. Using these data it was possible for the first time to probe the magnetic field in the steel of the barrel return yoke using reconstructed muon tracks. The CMS silicon tracker is located inside the superconducting coil of the CMS magnet.
17596373
Multi-monopoles, Magnetic Bags, BIons and the Monopole Cosmological Problem
By analogy with the multi-vortices, we show that also moltimonopoles become magnetic bags in the large n limit. This drastic simplification allows us to compute the spectrum and the profile functions by means of classical stabilization arguments. We consider in detail the case of the BPS magnetic bag and we find their moduli space. We then consider the possibility of cosmological production of multi-monopoles and we present a new possible solution of the monopole cosmological problem.
17078274
Stable vs. unstable vortices in SQCD
We give a topological classification of stable and unconfined massive particles and strings (and some instantons) in worldvolume theories of M5-branes and their dimensional reductions, generalizing Witten's classification of strings in SYM. In particular 4d = 2 SQCD softly broken to = 1 contains torsion (Douglas-Shenker) N-strings and nontorsion (Hanany-Tong) -strings. Some of the former are stable when the flavor symmetry is gauged, while those that are not stable confine quarks and in some vacua even dyons into baryons. The nontorsion strings are stable if and only if all colors are locked to flavors, which is weaker than the BPS condition. As a byproduct unstable string decay modes and approximate lifetimes are found. Cascading theories have no vortices stabilized by the topological charges treated here and in particular Gubser-Herzog-Klebanov axionic strings do not carry such a charge.
17004434
Baryons and Skyrmions in QCD with Quarks in Higher Representations
We study the baryonic sector of QCD with quarks in the two-index symmetric or antisymmetric representation. The minimal gauge invariant state that carries baryon number cannot be identified with the Skyrmion of the low-energy chiral effective Lagrangian. Mass, statistics, and baryon number do not match. We carefully investigate the properties of the minimal baryon in the large N limit and we find that it is unstable under formation of bound states with higher baryonic number. These states match exactly with the properties of the Skyrmion of the effective Lagrangian.0.
8082329
Confinement and localization on domain walls
We continue the studies of localization of the U(1) gauge fields on domain walls. Depending on dynamics of the bulk theory the gauge field localized on the domain wall can be either in the Coulomb phase or squeezed into flux tubes implying (Abelian) confinement of probe charges on the wall along the wall surface. First, we consider a simple toy model with one flavor in the bulk at weak coupling (a minimal model) realizing the latter scenario. We then suggest a model presenting an extension of the Seiberg-Witten theory which is at strong coupling, but all theoretical constructions are under full control if we base our analysis on a dual effective action. Finally, we compare our findings with the wall in a 'nonminimal' theory with two distinct quark flavors that had been studied previously. In this case the U(1) gauge field trapped on the wall is exactly massless because it is the Goldstone boson of a U(1) symmetry in the bulk spontaneously broken on the wall. The theory on the wall is in the Coulomb phase. We explain why the mechanism of confinement discussed in the first part of the paper does not work in this case, and strings aremore » not formed on the walls.« less
54188675
Baby Skyrme model, near-BPS approximations, and supersymmetric extensions
We study the baby Skyrme model as a theory that interpolates between two distinct BPS systems. For this a near-BPS approximation can be used which, however, involves a small deviation from each of the two BPS limits. We provide analytical explanation and numerical support for the validity of this approximation. We then study the set of all possible supersymmetric extensions of the baby Skyrme model with ${\cal N}=1$ and the particular ones with extended ${\cal N}=2$ supersymmetries and relate this to the above mentioned almost-BPS approximation.