Nuclear Theory·nucl-th

Tuesday·February 3, 2015

9 papers—5 primary·4 cross-listed

01
[Submitted on 31 Jan 2015]
Tunneling of atoms, nuclei and molecules
C.A. Bertulani
This is a brief review of few relevant topics on tunneling of composite particles and how the coupling to intrinsic and external degrees of freedom affects tunneling probabilities. I discuss the phenomena of resonant tunneling, different barriers seen by subsystems, damping of resonant tunneling by level bunching and continuum effects due to particle dissociation.
Comments:
8 pages, 8 figures, Contribution to the Proceedings of the International Workshop on Critical Stability, Santos, SP, Brazil, October 12-17, 2014. Ed. by Tobias Frederico
Subjects:
Nuclear Theory (nucl-th); Superconductivity (cond-mat.supr-con); Nuclear Experiment (nucl-ex); Quantum Physics (quant-ph)
arXiv:
1502.00074 [pdf]
Few Body Syst.(2015)·6 citations
02
[Submitted on 1 Feb 2015]
Low-energy proton capture reactions in the mass region 55-60
Saumi Dutta🇮🇳 · Dipti Chakraborty🇮🇳 · G. Gangopadhyay🇮🇳 · Abhijit Bhattacharyya🇮🇳
Low energy proton capture reactions in the mass 55-60 region are studied in a microscopic optical model. Nuclear density profile is calculated using the relativistic mean field theory. The DDM3Y interaction is folded with the theoretical density to obtain the proton-nucleus optical potential. A definite set of normalization parameters has been obtained for the concerned mass region by comparing with all available experimental data in this mass region. These parameters have been used to obtain proton capture rates for astrophysically important reactions in this mass region.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.00222 [pdf]
PRC(2015)·11 citations
03
[Submitted on 2 Feb 2015]
Quantifying properties of hot and dense QCD matter through systematic model-to-data comparison
Jonah E. Bernhard🇺🇸 · Peter W. Marcy🇺🇸 · Christopher E. Coleman-Smith🇺🇸 · Snehalata Huzurbazar🇺🇸 · Robert L. Wolpert🇺🇸 · Steffen A. Bass🇺🇸
We systematically compare an event-by-event heavy-ion collision model to data from the Large Hadron Collider. Using a general Bayesian method, we probe multiple model parameters including fundamental quark-gluon plasma properties such as the specific shear viscosity $η / s$ , calibrate the model to optimally reproduce experimental data, and extract quantitative constraints for all parameters simultaneously. The method is universal and easily extensible to other data and collision models.
Comments:
15 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1502.00339 [pdf]
PRC(2015)·112 citations
04
[Submitted on 2 Feb 2015]
Toward Universality in Similarity Renormalization Group Evolved Few-body Potential Matrix Elements
Brian Dainton🇺🇸
We first examine how T-matrix equivalence drives the flow of similarity renormalization group (SRG) evolved potential matrix elements to a universal form, with the ultimate goal of gaining insight into universality for three-nucleon forces. In agreement with observations made previously for Lee-Suzuki transformations, regions of universal potential matrix elements are restricted to where half-on-shell T-matrix equivalence holds, but the potentials must also reproduce binding energies. We find universality in local energy regions, reflecting a local decoupling by the SRG. To continue the study in the 3-body sector, we create a simple 1-D spinless boson "theoretical laboratory" for a dramatic improvement in computational efficiency. We introduce a basis-transformation, harmonic oscillator (HO) basis, which is used for current many-body calculations and discuss the imposed truncations. When SRG evolving in a HO-basis, we show that the evolved matrix elements, once transformed back into momentum-representation, differ from those when evolving with momentum representation. This is because the generator in each basis is not exactly the same due to the truncation, which creates evolution artifacts in the 3-body potential matrix elements. In the 2- body sector, this can be avoided by increasing the basis size, but it remains unclear whether this is possible in the 3-body sector, as truncation errors in the 3-body sector are more difficult to avoid, and the computational power required is greatly increased for three-body evolution.
Comments:
PhD thesis, Ohio State, 2015
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.00578 [pdf]
0 citations
05
[Submitted on 2 Feb 2015]
Collision Geometry and Flow in Uranium+Uranium Collisions
Andy Goldschmidt🇺🇸 · Zhi Qiu🇺🇸 · Chun Shen🇺🇸 · Ulrich Heinz🇺🇸
Using event-by-event viscous fluid dynamics to evolve fluctuating initial density profiles from the Monte-Carlo Glauber model for U+U collisions, we report a "knee"-like structure in the elliptic flow as a function of collision centrality, located near 0.5% centrality as measured by the final charged multiplicity. This knee is due to the preferential selection of tip-on-tip collision geometries by a high-multiplicity trigger. Such a knee structure is not seen in the STAR data. This rules out the two-component MC-Glauber model for initial energy and entropy production. An enrichment of tip-tip configurations by triggering solely on high-multiplicity in the U+U collisions thus does not work. On the other hand, using the Zero Degree Calorimeters (ZDCs) coupled with event-shape engineering, we identify the selection purity of body-body and tip-tip events in the full-overlap U+U collisions. With additional constraints on the asymmetry of the ZDC signals one can further increases the probability of selecting tip-tip events in U+U collisions.
Comments:
9 pages, 4 figures, Proceedings of WPCF 2014 in Gyöngyös, Hungary, Aug.25-29, 2014
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1502.00603 [pdf]
13 citations
06
[Submitted on 2 Feb 2015] (cross-list from hep-ph)
Top-down Holographic Glueball Decay Rates
F. Brünner🇦🇹 · D. Parganlija🇦🇹 · A. Rebhan🇦🇹
We present new results on the decay patterns of scalar and tensor glueballs in the top-down holographic Witten-Sakai-Sugimoto model. This model, which has only one free dimensionless parameter, gives semi-quantitative predictions for the vector meson spectrum, their decay widths, and also a gluon condensate in agreement with SVZ sum rules. The holographic predictions for scalar glueball decay rates are compared with experimental data for the widely discussed gluon candidates f0(1500) and f0(1710).
Comments:
9 pages, 2 figures, 2 tables; to appear in the Proceedings of the XIth Conference Quark Confinement and the Hadron Spectrum, St. Petersburg, September 8-12, 2014
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1502.00456 [pdf]
AIP Conf.Proc.(2016)·3 citations
07
[Submitted on 2 Feb 2015] (cross-list from nucl-th)
Elastic scattering of hadrons without optical theorem
Jiri Prochazka🇨🇿 · Vojtech Kundrat🇨🇿 · Milos V. Lokajicek🇨🇿
All contemporary phenomenological models of elastic hadronic scattering have been based on the assumption of validity of optical theorem that was overtaken from optics. It has been stated that it may be proven in particle physics. However, it will be shown that its derivation in the framework of unitary S-matrix theory (which is supposed to be the most general approach in this case) has been based on several requirements that do not correspond to the actual collision characteristics of two particles. It will be shown that especially in the case of short-ranged interaction (for which the theorem is used most frequently) it cannot be applied to. The analysis of corresponding collision experiments is to be done under new basic physical assumptions. The actual progress in the description of hadronic collision processes may exist only if the distribution of different initial states will be specified on the basis of impact parameter values of colliding particles and the dependence of collision probability on this parameter will be established, without limiting corresponding conclusions by the assumption of optical theorem validity from the very beginning.
Comments:
16 pages. arXiv admin note: substantial text overlap with arXiv:1403.1809
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1502.00468 [pdf]
3 citations
08
[Submitted on 2 Feb 2015] (cross-list from nucl-ex)
Event-by-event mean p_T fluctuations in pp and Pb-Pb collisions at the LHC
S. T. Heckel (for the ALICE Collaboration)🇩🇪
The ALICE detector at the LHC is used to study the properties of the Quark-Gluon Plasma produced in heavy-ion collisions. As a reference measurement, also the analysis of proton-proton (pp) collisions is very important. In the study presented here, event-by-event fluctuations of the mean transverse momentum are analysed in pp collisions at sqrt(s) = 0.9, 2.76 and 7 TeV, and Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV as a function of the charged-particle multiplicity. In both systems, dynamical fluctuations beyond the statistical expectation are observed. In pp collisions, no significant dependence on collision energy is found, even in comparison to inclusive results at much lower collision energies. Likewise, central A-A collisions show only little dependence on collision energy. The multiplicity dependence observed in peripheral Pb-Pb data is in agreement with that in pp collisions. Going to more central Pb-Pb collisions, a clear deviation from this trend is found, reaching a significant reduction of the fluctuations in most central collisions. Comparisons to Monte Carlo event generators show good agreement in pp, but rather large differences in Pb-Pb collisions.
Comments:
6 pages, 7 figures, proceedings to the XLIV International Symposium on Multiparticle Dynamics (ISMD) 2014, Bologna, Italy
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.00537 [pdf]
EPJ Web Conf.(2015)·9 citations
09
[Submitted on 2 Feb 2015] (cross-list from hep-lat)
Multichannel one-to-two transition amplitudes in a finite volume
Raúl A. Briceño🇺🇸 · Maxwell T. Hansen🇩🇪 · André Walker-Loud🇺🇸
We derive a model-independent expression for finite-volume matrix elements. Specifically, we present a relativistic, non-perturbative analysis of the matrix element of an external current between a one-scalar in-state and a two-scalar out-state. Our result, which is valid for energies below higher-particle inelastic thresholds, generalizes the Lellouch-Luscher formula in two ways: we allow the external current to inject arbitrary momentum into the system and we allow for the final state to be composed an arbitrary number of strongly coupled two-particle states with arbitrary partial waves (including partial-wave mixing induced by the volume). We also illustrate how our general result can be applied to some key examples, such as heavy meson decays and meson photo production. Finally, we point out complications that arise involving unstable resonance states, such as $B \to K^{*} ℓ^{+} ℓ^{-}$ when staggered or mixed-action/partially-quenched calculations are performed.
Comments:
Contribution to The 32nd International Symposium on Lattice Field Theory, 23-28 June, 2014, Columbia University New York, NY
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.00540 [pdf]
PoS(2015)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE