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At least 235 records · Page 13Linked to original sources

Three-body interactions in Fermi systems

We show that the contributions of three-quasiparticle interactions to normal Fermi systems at low energies and temperatures are suppressed by n_q/n compared to two-body interactions, where n_q is the density of excited or added quasiparticles and n is the ground-state density. For finite Fermi systems, three-quasiparticle contributions are suppressed by the corresponding ratio of particle numbers N_q/N. This is illustrated for polarons in strongly interacting spin-polarized Fermi gases and for valence neutrons in neutron-rich calcium isotopes.

nucl-th↗

Di-muon measurements in CBM experiment at FAIR

The compressed baryonic matter (CBM) experiment at the future FAIR accelerator facility near Darmstadt, Germany, aims at the investigation of baryonic matter at highest net baryon densities but moderate temperatures, by colliding heavy-ions at beam energies from 10 to 45 A GeV. The research program comprises the exploration of some basic landmarks of the QCD phase diagram like transitions from hadronic to partonic phase, the region of first order de-confinement as well as chiral phase transition, and the critical end point. The proposed key observables include the measurement of low mass vector mesons and charmonia, which can be detected via their decay into the di-lepton channel. As the decayed leptons leave the hot and dense fireball without further interactions, hence they provide almost unscathed information about the interior of the collision zone where they are being created. In this paper, we discuss the physics motivation, detector concepts, and the feasibility studies in the di-muon measurements for central Au + Au collisions, with a special reference to the detailed simulation activities performed by the CBM muon group.We also discuss the R&D activities of detector in brief.

nucl-ex↗

Nucleon Momentum Decomposition in QCD

~Based on the gauge invariant quark canonical momentum we construct two theoretically possible decompositions of nucleon momentum to those of quarks and gluons. We predict that either 6% or 21% of nucleon momentum is carried by gluons, depending on what type of gluons are in nucleons. We clarify the existing confusions on this problem and discuss the physical implications of our result on the proton spin crisis problem.

nucl-th↗

Cross section in deuteron-proton elastic scattering at 1.25 GeV/u

First results of the differential cross section in dp elastic scattering at 1.25 GeV/u measured with the HADES over a large angular range are reported. The obtained data corresponds to large transverse momenta, where a high sensitivity to the two-nucleon and three-nucleon short-range correlations is expected.

nucl-ex↗

Off-Fermi Shell Nucleons in Superdense Asymmetric Nuclear Matter

Recent observations of the strong dominance of proton-neutron (pn) relative to pp and nn short-range correlations (SRCs) in nuclei indicate on possibility of unique new condition for asymmetric high density nuclear matter, in which the pp and nn interactions are suppressed while the pn interactions are enhanced due to tensor interaction. We demonstrate that for sufficiently asymmetric case and high densities the momentum distribution of the smaller p-component is strongly deformed with protons increasingly populating the momentum states beyond the Fermi surface. This result is obtained by extracting the probabilities of two-nucleon (2N) SRCs from the analysis of the experimental data on high momentum transfer inclusive electro-nuclear reactions. We fitted the extracted probabilities as a function of nuclear density and asymmetry and used the fit to estimate the fractions of the off-Fermi shell nucleons in the superdense nuclear matter relevant to neutron stars. Our results indicate that starting at three nuclear saturation densities the protons with fractional densities 1/9 will populate mostly the high momentum tail of the momentum distribution while only 2% of the neutrons will do so. We discuss the implications of this condition for neutron stars and emphasize that it may be characteristic to any asymmetric two component Fermi system with suppressed central and enhanced short-range tensor interactions between the two components.

nucl-th↗

Order of precedence and age of Y-DNA haplotypes

A simple method, inspired by procedures used in physics of nuclear multifragmentation, allows to establish order of precedence and age of pairs of haplotypes separated by one mutation. For both haplotypes of the pair, searches for existing haplotypes, differing by increasing number of mutations, are carried out using a database. The resulting ratios of frequences of haplotypes, found at given mutation distances, are compared to calculated probability ratios. The order of precedence and age of the pair of haplotypes can be deduced when the resulting ratios follow hyperbolic dependence. Method can be used with relatively small and not necessarily complete samples, using publicly accessible databases.

physics.data-an↗

Leading-order hadronic contribution to g-2 from lattice QCD

We calculate the leading-order hadronic correction to the anomalous magnetic moments of each of the three charged leptons in the Standard Model: the electron, muon and tau. Working in two-flavor lattice QCD, we address essentially all sources of systematic error: lattice artifacts, finite-size effects, quark-mass extrapolation, momentum extrapolation and disconnected diagrams. The most significant remaining systematic error, the exclusion of the strange and charm quark contributions, will be addressed in our four-flavor calculation. We achieve a statistical accuracy of 2% or better for the physical values for each of the three leptons and the systematic errors are at most comparable.

hep-lat↗

Participant-like scaling behavior of multiplicity and charged hadron spectra in relativistic heavy ion collisions

We present a method for parameterizing the charged particle multiplicity and charged hadron spectra from heavy ion data with a simple, Glauber-inspired, model. The basis of this model is derived from the observation of leading hadrons in $pp$ collisions and the number of interactions calculated by a Glauber model. Singly hit and multiply hit nucleons are treated as different sub-components of the same collision. With this scheme, for fixed sub-component yields, we find that the multiplicity and charged hadron spectra can be reproduced, without the need for large suppression at high-p$_T$. Suppression is still observed, in the low- to intermediate-p$_T$ region, but this is confined to suppression of surface emission partons. At high-p$_T$, the suppression disappears entirely, leaving only a possible Cronin-type enhancement. The suppression observed in 200GeV collisions is found to be the same for 62.4GeV data.

nucl-ex↗

Four pedagogic exercises

This article describes four innovative pedagogical exercises: (i) The expression for relation between cross sections in the laboratory and the centre of mass systems provided in text books assumes zero or low Q values which needs to be corrected for the most general case when Q value of the reaction is not negligible compared to the masses of interacting nuclei. The general expression derived here can be used for elastic and inelastic cases involving zero, low or even very high Q values. (ii) The equation of oscillatory motion of a massive surface put horizontally on two wheels rotating with equal and opposite angular velocities is established. The time period of oscillation is related to the coefficient of dynamic friction between the surface and the wheels which facilitates the measurement of the coefficient of dynamic friction. (iii) The equation of motion of a fixed torque mass shedding vehicle moving against friction and its velocity at any instant of time are derived. This example is equivalent to motion of a mass shedding rocket moving by applying fixed force against atmospheric friction. (iv) The equation of the path of a missile directed at every instant of time towards a rectilinearly moving target and time taken to hit the target are derived. It provides equation of path for asteroid and comet destructing missiles as conceptualized by NASA projects.

physics.class-ph↗

Production of antinuclei in pp collisions at \sqrt{s} = 7 TeV with ALICE at the LHC

First results of ALICE on the production of nuclei and antinuclei in pp collisions at \surd s = 7 TeV are presented. These particles are identified using the energy loss (dE/dx) measurements in the Time Projection Chamber. The Inner Tracking System allows a precise determination of the event vertex, by which primary and secondary particles are well separated. The high statistics of over 350 M events give a significant number of light nuclei and antinuclei such as (anti)deuterons, (anti)tritons, (anti)Helium3 and possibly (anti)hypertritons. The study of nuclei and antinuclei will help to understand their production mechanisms. Antinuclei production as a function of particle multiplicity in an event is discussed in this respect. Various particle ratios obtained from these collisions using predictions from a statistical model are also presented.

nucl-ex↗

Measurement of airborne radioactivity from the Fukushima reactor accident in Tokushima, Japan

The airborne radioactive isotopes from the Fukushima Daiichi nuclear plan t was measured in Tokushima, western Japan. The continuous monitoring has been carried out in Tokushima. From March 23, 2011 the fission product $^{131}$I was observed. The radioisotopes $^{134}$Cs and $^{137}$Cs were also observed in the beginning of April. However the densities were extremely smaller than the Japanese regulation of radioisotopes.

nucl-ex↗

Partial Dynamical Symmetry in the f7/2 and g9/2 shell

We discuss partial dynamical symmetries which occur in single j shell calculations mostly for high spin states for systems of three or four particles (holes). The relevant nuclei are 43Ti,43Sc, 44Ti, 52Fe,53Fe, 53Co,96Cd,97Cd, and 97In.

nucl-th↗

Dependence of elliptic flow on transverse momentum in $\sqrt{\mathrm{\it s_{NN}}}=200$ GeV Au-Au and $\sqrt{\mathrm{\it s_{NN}=2.76$ TeV Pb-Pb collisions

We investigate the dependence of elliptic flows $v_2$ on transverse momentum $P_T$ for charged hadrons produced in nucleus-nucleus collisions at high energy by using a multi-source ideal gas model which includes the interaction contribution of the emission sources. Our calculated results are approximately in agreement with the experimental data over a wider $P_T$ range from the STAR and ALICE Collaborations. It is found that the expansion factor increases linearly with the impact parameter from most central (0-5%) to mid-peripheral (35-40%) collisions.

nucl-th↗

On problems of experimental determination of reliable values of nucleus parameters at low excitation energy - Ni-60 as an example

The reanalysis of the published experimental data from reaction Co-59(p,2gamma)Ni-60 was performed. The region of the most probable values of level density and radiative strength functions of cascade gamma-transitions was determined. The obtained data were rather precisely approximated by the V.M. Strutinsky model and semi-phenomenological model - for strength functions. The region of appearance and magnitude of maximal errors of the calculated cross-section of nucleon emission in evaporation spectra in traditional methods of their analysis were determined as well. There was for the first time obtained methodically correct information on the radiation strength function of primary gamma-transitions in diapason of neutron binding energy with averaging over large set of initial levels.

nucl-ex↗

Derivation and quantitative analysis of the differential self-interrogation Feynman-alpha method

A stochastic theory for a branching process in a neutron population with two energy levels is used to assess the applicability of the differential self-interrogation Feynman-alpha method by numerically estimated reaction intensities from Monte Carlo simulations. More specifically, the variance to mean or Feynman-alpha formula is applied to investigate the appearing exponentials using the numerically obtained reaction intensities.

nucl-ex↗

Nuclear reaction rates and the primordial nucleosynthesis

The theoretical predictions of the primordial abundances of elements in the big-bang nucleosynthesis (BBN) are dominated by uncertainties in the input nuclear reaction rates. We investigate the effect of modifying these reaction rates on light element abundance yields in BBN by replacing the thirty-five reaction rates out of the existing eighty-eight. We have studied these yields as functions of evolution time or temperature. We find that using these new reaction rates results in only a little increase in helium mass fraction over that obtained previously in BBN calculations. This allows insights into the role of the nuclear reaction rates in the setting of the neutron-to-proton ratio during the BBN epoch. We observe that even with considerable nuclear physics uncertainties, most of these nuclear reactions have minimal effect on the standard BBN abundance yields of $^6$Li and $^7$Li.

nucl-th↗

Comment on "Nuclear structure corrections in muonic deuterium"

A recent letter [1] investigated the effects of deuteron polarizability in the mu D atom. The importance of understanding this atom has been heightened because of the possible light it could shed on the proton radius puzzle. Here we confirm, clarify, and emphasize the significance of the result [1] that the effects of the third Zemach moment are canceled by part of the deuteron polarizability effects. 1. K. Pachucki, Phys. Rev. Lett. 106, 193007 (2011)

physics.atom-ph↗

Studies of Jet Quenching in HI Collisions at CMS

Jet production in PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV was studied using the CMS detector at the LHC, using a data sample corresponding to an integrated luminosity of 6.7 inverse microbarn. Dijets were reconstructed using the CMS calorimeters, and a significant energy imbalance was observed between the leading jet and the away-side jet with increasing centrality. Correlation studies of jets and tracks reveal that the energy of the away-side jet is redistributed to lower pt and wider angle outside of the jet cone.

nucl-ex↗