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Nuclear Experiment

New submissions

[ total of 13 entries: 1-13 ]
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New submissions for Tue, 20 Feb 18

[1]  arXiv:1802.06277 [pdf]
Title: Neutron lifetime, dark matter and search for sterile neutrino
Comments: 20 pages, 18 figures
Subjects: Nuclear Experiment (nucl-ex)

A review is focused on experimental measurements on neutron lifetime. The latest measurements with a gravitational trap (PNPI NRC KI) and a magnetic trap (LANL, USA) confirmed PNPI result of 2005. The results of measurements with storage of ultra cold neutrons are in agreement, yet, there is discrepancy with a beam experiment by $3.5{\sigma}$ (1% of decay probability), which is discussed in literature as "neutron anomaly" along with the ideas of explaining it by decay into dark matter partially. The second part of the paper is devoted to so called "reactor antineutrino anomaly", which refers to deficiency of the measured flux of antineutrino from reactor in respect to the calculated flux by $3{\sigma}$(deviation by 6.6%). Specific feature of the proposal in this paper lies in the fact that both anomalies can be accounted for by one and the same phenomenon of oscillation in baryon sector between a neutron and a neutron of dark matter $n{\rightarrow}n'$ with mass $m_{n'}$, somewhat less than mass $m_n$ of an ordinary neutron. Calculations of the proposed model require one free parameter: mass difference $m_n-m_{n'}$ if one normalizes probability of oscillations for a free neutron on "neutron anomaly" 1%, then, having succeeded to interpret 6.6% of neutron anomaly in calculations, one can determine mass difference. According to preliminary estimations, the mass difference is $m_n-m_{n'}{\approx}$ 3 MeV. However, the analysis of cumulative yields of isotopes occurs in fission fragments was performed and it does not confirm possibility of existence of additional decay channel with emission of dark matter neutron with mass difference $m_n-m_{n'}{\approx}$ 3 MeV. The result of the analysis is the conclusion that for mirror neutrons the region of the mass difference $m_n-m_{n'} {\geq}$ 3 MeV is closed. The region of the mass difference $m_n-m_{n'}{\leq}$ 2 MeV turned out to be not closed.

[2]  arXiv:1802.06541 [pdf, other]
Title: Electroweak probes with ATLAS
Comments: 6 pages, 9 figures
Subjects: Nuclear Experiment (nucl-ex)

Measuring electroweak bosons in relativistic heavy ion collisions at high energy provide an opportunity to understand temporal evolution of the quark-gluon plasma created in such collisions by constraining the initial state of the interaction. Due to lack of color charges the bosons and or particles produced in their leptonic decays are unaffected by the quark-gluon plasma and therefore preserve the information about the very early stage of the collision when they were born. This singles electroweak bosons as a unique and very interesting class of observables in heavy ion collisions. The ATLAS experiment at LHC measures production of electroweak bosons in pp, p+Pb, and Pb + Pb collisions systems. A review of the existing results is given in this proceeding that includes studies made with isolated photons to constraint kinematic properties and flavour composition of associated jets, measurements of W and Z bosons used to estimate nuclear modification of parton distribution function and the production rates of the bosons used to verify geometric models implied to estimate event centrality. A novel analysis on measuring two-particle correlations in pp collisions where the Z boson is registered is also discussed in the proceeding. This is the first attempt to break into the initial geometry of the pp collisions by constraining the impact parameter with a hard scattering process. It shows that the strength of the two particle correlations in such collision is 1.08+/-0.06 above the inclusive. To make the measurement ATLAS solves the technical problem of measuring the underlying event in high pileup condition.

[3]  arXiv:1802.06595 [pdf, ps, other]
Title: Acoustic scaling of linear and mode-coupled anisotropic flow; implications for precision extraction of the specific shear viscosity
Authors: Peifeng Liu, Roy A. Lacey (SUNY Stony Brook Chemistry Dept & SUNY Stony Brook Physics Dept.)
Comments: 5 pages, 3 figs., submitted for publication
Subjects: Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)

The scaling properties of the $\mathrm{n^{th}}$-order linear flow coefficients $\mathrm{v^L_n \, (n=2,3,4,5)}$, and the corresponding nonlinear mode-coupled ($\mathrm{mc}$) coefficients $\mathrm{v^{mc}_{4,(2,2)}}$, $\mathrm{v^{mc}_{5,(2,3)}}$, $\mathrm{v^{mc}_{6,(3,3)}}$ and $\mathrm{v^{mc}_{6,(2,2,2)}}$, are studied for Pb+Pb collisions at $\sqrt{s_{_{\rm NN}}} = 2.76$ TeV. Both sets of coefficients indicate a common acoustic scaling pattern of exponential viscous modulation, at a rate proportional to the square of the harmonic numbers and the mean transverse momenta (respectively), and inversely proportional to the cube root of the charged particle multiplicity ($\mathrm{(N_{ch})^{1/3}}$), that characterizes the dimensionless size of the systems produced in the collisions. These patterns and their associated scaling parameters, provide new stringent constraints for eccentricity independent estimates of the specific shear viscosity ($\eta/s$) of the matter produced in the collisions, as well as simultaneous extraction of the initial-state eccentricity spectrum.

[4]  arXiv:1802.06746 [pdf, ps, other]
Title: Differential Cross Section for $γd \rightarrow ωd$ using CLAS at Jefferson Lab
Authors: T. Chetry (1), K. Hicks (1), N. Compton (1), M. Sargsian (2) (the CLAS Collaboration) ((1) Ohio University, Athens, Ohio (2) Florida International University, Miami, Florida)
Comments: 8 pages, 5 figures
Subjects: Nuclear Experiment (nucl-ex); High Energy Physics - Experiment (hep-ex)

The cross section for coherent $\omega$-meson photoproduction off the deuteron has been measured for the first time as a function of the momentum transfer $t = (P_{\gamma}-P_{\omega})^2$ and photon energy $E_{\gamma}$ using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cross sections are measured in the energy range $1.4 < E_{\gamma} < 3.4$ GeV. A model based on $\omega-N$ rescattering is consistent with the data at low and intermediate momentum transfer, $|t|$. For $2.8 < E_{\gamma} < 3.4$ GeV, the total cross-section of $\omega-N$ scattering is 30-40 mb in the framework of Vector Meson Dominance.

[5]  arXiv:1802.06752 [pdf]
Title: Multifractal analysis of charged particle multiplicity distribution in the framework of Renyi entropy
Subjects: Nuclear Experiment (nucl-ex)

A study of multifractality and multifractal specific heat has been carried out for the produced shower particles in nuclear emulsion detector for 16O-AgBr, 28Si-AgBr and 32S-AgBr interactions at 4.5AGeV/c in the framework of Renyi entropy. Experimental results have been compared with the prediction of UrQMD model. Our analysis reveals the presence of multifractality in the multiparticle production process in high energy nucleus-nucleus interactions. Degree of multifractality is found to be higher for the experimental data and it increases with the increase of projectile mass.

Cross-lists for Tue, 20 Feb 18

[6]  arXiv:1801.07631 (cross-list from hep-ph) [pdf, ps, other]
Title: Spin-1 particles and perturbative QCD
Authors: J. P. B. C. de Melo (LFTC - Cruzeiro do Sul), T. Frederico (Instituto Tecnológico de Aeronáutica - ITA), Chueng -R. Ji (Departament of Physics, North Carolina State University, NCSU)
Comments: 7 pages, 4 figures, Few-Body latex style. Contribuition to the Light-Cone 2017, 18-22 September, 2017, Mumbai, India. Submitted to Few-Body Systems
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); High Energy Physics - Theory (hep-th); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)

Due to the angular condition in the light-front dynamics (LFD), the extraction of the electromagnetic form factors for spin-1 particles can be uniquely determined taking into account implicitly non-valence and/or the zero-mode contributions to the matrix elements of the electromagnetic current. No matter which matrix elements of the electromagnetic current is used to extract the electromagnetic form factors, the same unique result is obtained. As physical observables, the electromagnetic form factors obtained from matrix elements of the current in LFD must be equal to those obtained in the instant form calculations. Recently, the Babar collaboration \cite{Aubert2008} has analyzed the reaction $e^+ e^-\rightarrow \rho^+ + \rho^-$ at $\sqrt{s}=10.58 GeV$ to measure the cross section as well as the ratios of the helicity amplitudes $F_{\lambda'\lambda}$. We present our recent analysis of the Babar data for the rho meson considering the angular condition in LFD to put a stringent test on the onset of asymptotic perturbative QCD and predict the energy regime where the subleading contributions are still considerable.

[7]  arXiv:1802.06078 (cross-list from nucl-th) [pdf, other]
Title: Decay Modes of the Hoyle State in $^{12}C$
Comments: 6 pages, 2 figures, accepted by Phys. Lett. B
Subjects: Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)

Recent experimental results give an upper limit less than 0.043\% (95\% C.L.) to the direct decay of the Hoyle state into 3$\alpha$ respect to the sequential decay into $^8${Be}+$\alpha$. We performed one and two-dimensional tunneling calculations to estimate such a ratio and found it to be more than one order of magnitude smaller than experiment depending on the range of the nuclear force. This is within high statistics experimental capabilities. Our results can also be tested by measuring the decay modes of high excitation energy states of $^{12}$C where the ratio of direct to sequential decay might reach 10\% at $E^*$($^{12}$C)=10.3 MeV. The link between a Bose Einstein Condensate (BEC) and the direct decay of the Hoyle state is also addressed. We discuss a hypothetical `Efimov state' at $E^*$($^{12}$C)=7.458 MeV, which would mainly {\it sequentially} decay with 3$\alpha$ of {\it equal energies}: a counterintuitive result of tunneling. Such a state, if it would exist, is at least 8 orders of magnitude less probable than the Hoyle's, thus below the sensitivity of recent and past experiments.

[8]  arXiv:1802.06243 (cross-list from hep-ph) [pdf, ps, other]
Title: Twist-3 GPDs in Deeply-Virtual Compton Scattering
Comments: 25 pages
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Experiment (nucl-ex)

The sub-leading power of the scattering amplitude for deeply-virtual Compton scattering (DVCS) off the nucleon contains leading-twist and twist-3 generalized parton distributions (GPDs). We point out that in DVCS, at twist-3 accuracy, one cannot address any individual twist-3 GPD. Accessible are exclusively linear combinations involving both vector and axial-vector twist-3 GPDs. This implies, in particular, that in DVCS there is no direct access to the (kinetic) orbital angular momentum of quarks through twist-3 GPDs. Moreover, using the quark-target model, we find that twist-3 GPDs can be discontinuous. The discontinuities however vanish in the DVCS amplitude, which further supports the hypothesis of factorization at twist-3 accuracy.

Replacements for Tue, 20 Feb 18

[9]  arXiv:1703.04944 (replaced) [pdf, ps, other]
Title: Kinetic freeze-out temperatures in central and peripheral collisions: Which one is larger?
Comments: 22 pages, 11 figures. Nuclear Science and Techniques, accepted
Subjects: Nuclear Theory (nucl-th); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
[10]  arXiv:1709.00882 (replaced) [pdf]
Title: Projectile Fragmentation of relativistic nuclei in peripheral Collisions
Comments: arXiv admin note: text overlap with arXiv:nucl-ex/0604007 by other authors
Subjects: Nuclear Experiment (nucl-ex)
[11]  arXiv:1711.09587 (replaced) [pdf, other]
Title: Signatures of octupole correlations in neutron-rich odd-mass barium isotopes
Comments: 10 pages, 7 figures, 9 tables
Journal-ref: Physical Review C 97, 024317 (2018)
Subjects: Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
[12]  arXiv:1801.01764 (replaced) [pdf, ps, other]
Title: Bulk Properties of the Matter Produced at Energies of the Beam Energy Scan Program
Comments: 9 pages, 8 figures. 1 figure added, minor corrections, version published in Phys. Rev. C
Subjects: Nuclear Theory (nucl-th); High Energy Physics - Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
[13]  arXiv:1801.08940 (replaced) [pdf, other]
Title: Precision mass measurements on neutron-rich rare-earth isotopes at JYFLTRAP - reduced neutron pairing and implications for the $r$-process calculations
Comments: 8 pages, 3 figures, submitted to Phys. Rev. Lett. Aug 8, 2017; revised Nov 3, 2017; revised Feb 17, 2018
Subjects: Nuclear Experiment (nucl-ex); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
[ total of 13 entries: 1-13 ]
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