7991709
Measurement of inelastic, single- and double-diffraction cross sections in proton–proton collisions at the LHC with ALICE
Measurements of cross sections of inelastic and diffractive processes in proton–proton collisions at LHC energies were carried out with the ALICE detector. The fractions of diffractive processes in inelastic collisions were determined from a study of gaps in charged particle pseudorapidity distributions: for single diffraction (diffractive mass MX<200 GeV/c2) $\sigma_{\mathrm{SD}}/\sigma_{\mathrm {INEL}} = 0.21 \pm 0.03, 0.20^{+0.07}_{-0.08}$, and $0.20^{+0.04}_{-0.07}$, respectively at centre-of-mass energies $\sqrt{s} = 0.9, 2.76\mbox{, and }7~\mbox{TeV}$; for double diffraction (for a pseudorapidity gap Δη>3) σDD/σINEL=0.11±0.03,0.12±0.05, and $0.12^{+0.05}_{-0.04}$, respectively at $\sqrt{s} = 0.9, 2.76\mbox{, and }7~\mbox{TeV}$. To measure the inelastic cross section, beam properties were determined with van der Meer scans, and, using a simulation of diffraction adjusted to data, the following values were obtained: $\sigma_{\mathrm{INEL}} = 62.8^{+2.4}_{-4.0} (\mathrm{model}) \pm1.2 (\mathrm{lumi})$ mb at $\sqrt{s} = 2.76\ \mbox{TeV}$ and $73.2^{+2.0}_{-4.6} (\mathrm{model}) \pm2.6 (\mathrm{lumi})~\mbox{mb}$ at $\sqrt{s} = 7\ \mbox{TeV}$. The single- and double-diffractive cross sections were calculated combining relative rates of diffraction with inelastic cross sections. The results are compared to previous measurements at proton–antiproton and proton–proton colliders at lower energies, to measurements by other experiments at the LHC, and to theoretical models.
119253123
Underlying Event measurements in pp collisions at $ \sqrt {s} = 0.9 $ and 7 TeV with the ALICE experiment at the LHC
A bstractWe present measurements of Underlying Event observables in pp collisions at $ \sqrt {s} = 0.9 $ and 7TeV. The analysis is performed as a function of the highest charged-particle transverse momentum pT,LT in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different pT thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2–3 between the lower and higher collision energies, depending on the track pT threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and Phojet. On average, all models considered underestimate the multiplicity and summed pT in the Transverse region by about 10–30%.
13915263
A NUMERICAL STUDY OF IMPROVED QUARK ACTIONS ON ANISOTROPIC LATTICES
Tadpole improved Wilson quark actions with clover terms on anisotropic lattices are studied numerically. Using asymmetric lattice volumes, the pseudoscalar meson dispersion relations are measured for eight lowest lattice momentum modes with quark mass values ranging from the strange to the charm quark with various values of the gauge coupling β and three different values of the bare speed of light parameter ν. These results can be utilized to extrapolate or interpolate to obtain the optimal value for the bare speed of light parameter νopt(m) at a given gauge coupling for all bare quark mass values m. In particular, the optimal values of ν at the physical strange and charm quark mass are given for various gauge couplings. The lattice action with these optimized parameters can then be used to study physical properties of hadrons involving either light or heavy quarks.
120902364
A NUMERICAL STUDY OF IMPROVED WILSON QUARK ACTIONS ON ANISOTROPIC LATTICES
Tadpole improved Wilson quark actions with clover terms on anisotropic lattices are studied numerically. Using asymmetric lattice volumes, the pseudo-scalar meson dispersion relations are measured for 8 lowest lattice momentum modes with quark mass values ranging from the strange to the charm quark with various values of the gauge coupling β and 3 different values of the bare speed of light parameter ν. These results can be utilized to extrapolate or interpolate to obtain the optimal value for the bare speed of light parameter νopt(m) at a given gauge coupling for all bare quark mass values m. In particular, the optimal values of ν at the physical strange and charm quark mass are given for various gauge couplings. The lattice action with these optimized parameters can then be used to study physical properties of hadrons involving either light or heavy quarks.
15518847
Spontaneous Broken Local Conformal Symmetry and Dark Energy
The local conformal symmetry is spontaneously broken down to the Local Lorentz invariance symmetry through the approach of nonlinear realization. The resulting effective Lagrangian, in the unitary gauge, describes a cosmological vector field non-minimally coupling to the gravitational field. As a result of the Higgs mechanism, the vector field absorbs the dilaton and becomes massive, but with an independent energy scale. The Proca type vector field can be modelled as dark energy candidate. The possibility that it further triggers Lorentz symmetry violation is also pointed out.
119305549
Scaling of the CKM Matrix in the 5D MSSM
We discuss a five-dimensional minimal supersymmetric standard model compactified on a ${S}^{1}/{Z}_{2}$ orbifold, looking at, in particular, the one-loop evolution equations of the Yukawa couplings for the quark sector and various flavor observables. Different possibilities for the matter fields are discussed; that is, where they are in the bulk or localized to the brane. The two possibilities give rise to quite different behaviors. By studying the implications of the evolution with the renormalization group of the Yukawa couplings and of the flavor observables, we find that, for a theory that is valid up to the unification scale, the case where fields are localized to the brane, with a large $\mathrm{tan}﻿\ensuremath{\beta}$, would be more easily distinguishable from other scenarios.
119199648
Renormalization Invariants and Quark Flavor Mixings
A set of renormalization invariants is constructed using approximate, two-flavor, analytic solutions to RGE's. These invariants exhibit explicitly the correlation between quark flavor mixings and mass ratios from electroweak scale to GUT scale in the context of the SM, DHM and MSSM models. The well-known empirical relations θ23 ∝ ms/mb, θ13 ∝ md/mb at electroweak scale can thus be understood as the result of renormalization evolution toward the infrared point. The validity of this approximation is evaluated by comparing the numerical solutions with the analytical approach. It is found that the scale dependence of these quantities for general three-flavor mixing follows closely these invariants up to the GUT scale.