Search results for "Observable"
showing 10 items of 634 documents
Spin correlations at the Z peak. A probe to the Z′ mass
1992
Abstract The interactions of a new heavy gauge boson are fixed by its coupling to matter and by its mass and its mixing with the Z 0 . Until now LEP has only constrained the Z′ mixing. However, there is one observable (and only one), the P - and T -odd transverse-normal spin correlation in ττ production, which fully and independently of its mixing measures the Z′ mass at the Z peak. For M z′ ∼ 130 GeV the Z′ contribution to this observable is typically of the same order as the standard model contribution.
J/ production as a function of charged-particle pseudorapidity density in p–Pb collisions at
2017
We report measurements of the inclusive J/ψ yield and average transverse momentum as a function of charged-particle pseudorapidity density dNch/dη in p–Pb collisions at sNN=5.02TeV with ALICE at the LHC. The observables are normalised to their corresponding averages in non-single diffractive events. An increase of the normalised J/ψ yield with normalised dNch/dη, measured at mid-rapidity, is observed at mid-rapidity and backward rapidity. At forward rapidity, a saturation of the relative yield is observed for high charged-particle multiplicities. The normalised average transverse momentum at forward and backward rapidities increases with multiplicity at low multiplicities and saturates beyo…
CP violation and limits on New Physics including recent B-s measurements
2007
We analyse present constraints on the SM parameter space and derive, in a model independent way, various bounds on New Physics contributions to $B_d^0$--$\bar B_d^0$ and $B_s^0$--$\bar B_s^0$ mixings. Our analyses include information on a large set of asymmetries, leading to the measurement of the CKM phases $\gamma$ and $\bar\beta$, as well as recent data from D0 and CDF related to the $B_s^0$--$\bar B_s^0$ system such as the measurement of $\Delta M_{B_s}$, $A_{SL}$ and $\Delta\Gamma_{s}^{CP}$. We examine in detail several observables such as the asymmetries $A_{sl}^d$, $A_{SL}$, the width differences $\Delta\Gamma_{d}$ and $\Delta\Gamma_{s}^{CP}$ and discuss the r\^ole they play in estab…
Testing refined shell-model interactions in thesdshell: Coulomb excitation ofNa26
2015
Background: Shell-model calculations crucially depend on the residual interaction used to approximate the nucleon-nucleon interaction. Recent improvements to the empirical universal $sd$ interaction (USD) describing nuclei within the $sd$ shell yielded two new interactions---USDA and USDB---causing changes in the theoretical description of these nuclei.Purpose: Transition matrix elements between excited states provide an excellent probe to examine the underlying shell structure. These observables provide a stringent test for the newly derived interactions. The nucleus $^{26}\mathrm{Na}$ with 7 valence neutrons and 3 valence protons outside the doubly-magic ${}^{16}\mathrm{O}$ core is used a…
General Multipole Expansion of Polarization Observables in Deuteron Electrodisintegration
2002
Formal expressions are derived for the multipole expansion of the structure functions of a general polarization observable of exclusive electrodisintegration of the deuteron using a longitudinally polarized beam and/or an oriented target. This allows one to exhibit explicitly the angular dependence of the structure functions by expanding them in terms of the small rotation matrices $d^j_{m'm}(\theta)$, whose coefficients are given in terms of the electromagnetic multipole matrix elements. Furthermore, explicit expressions for the coefficients of the angular distributions of the differential cross section including multipoles up to $L_{max}=3$ are listed in tabular form.
The role of the neutron electric form factor ind(e, e? N)N including polarization observables
1988
The influence of the neutron electric form factor on various observables in two-body break-up of deuterons by electrons such as differential cross section, beam, target and beam-target asymmetries and outgoing nucleon polarization as well is investigated for different kinematic regions. The electron-deuteron vector asymmetryAedV and the outgoing nucleon polarization component P′x(n) are the most promising observables in and off the quasi-free region for a determination ofGEn. Also the single polarization observablesAdT and Py0(p) and the double polarization observable P′z(n) show significant influences fromGEn.
Nucleon electromagnetic form factors in the timelike region
2012
The electromagnetic form factors of the proton and the neutron in the timelike region are reviewed. In view of the forthcoming experimental projects devoted to investigate these observables, we present the current status of the field and we emphasize the relevant role, that accurate measurements, refined phenomenological analyses, as well as microscopic models will play with the goal of achieving deeper insights into the structure of the nucleon and its inner dynamics.
Effects of partial thermalization on HBT interferometry
2009
Hydrodynamical models have generally failed to describe interferometry radii measured at RHIC. In order to investigate this ``HBT puzzle'', we carry out a systematic study of HBT radii in ultrarelativistic heavy-ion collisions within a two-dimensional transport model. We compute the transverse radii $R_o$ and $R_s$ as functions of $p_t$ for various values of the Knudsen number, which measures the degree of thermalization in the system. For realistic values of the Knudsen number estimated from $v_2$ data, we obtain $R_o/R_s \simeq 1.2$, much closer to data than standard hydrodynamical results. Femtoscopic observables vary little with the degree of thermalization. Azimuthal oscillations of th…
EFFECTIVE FIELD THEORY APPROACH TO THE NUCLEON–NUCLEON INTERACTION REVISITED
2006
It is argued that Weinberg's approach to the nucleon–nucleon (NN) interaction problem within effective field theory provides a consistent power counting for renormalized diagrams. Within this scheme the NN potential is organized as an expansion in terms of small quantities like small external momenta and the pion mass (divided by the characteristic large scale of the effective theory). Physical observables to any given order in these small quantities are calculated from the solutions of the Lippmann–Schwinger (or Schrödinger) equation.
Fluctuating parts of nuclear ground state correlation energies
2013
Background: Heavy atomic nuclei are often described using the Hartree-Fock-Bogoliubov (HFB) method. In principle, this approach takes into account Pauli effects and pairing correlations while other correlation effects are mimicked through the use of effective density-dependent interactions. Purpose: Investigate the influence of higher order correlation effects on nuclear binding energies using Skyrme's effective interaction. Methods: A cut-off in relative momenta is introduced in order to remove ultraviolet divergences caused by the zero-range character of the interaction. Corrections to binding energies are then calculated using the quasiparticle-random-phase approximation (QRPA) and secon…