Nuclear Theory·nucl-th

Tuesday·August 4, 2015

9 papers—3 primary·6 cross-listed

04
[Submitted on 1 Aug 2015] (cross-list from hep-lat)
Excited-state contamination in nucleon correlators from chiral perturbation theory
Brian C. Tiburzi🇺🇸
Techniques to compute hadron properties from lattice QCD rely upon the limit of long time separation. For baryons, the signal-to-noise problem often restricts one to time separations that are not ideally long, and for which couplings to excited states can obstruct the isolation of ground-state baryon properties. We consider excited-state contamination in nucleon two- and three-point functions. Using chiral perturbation theory, we determine couplings to pion-nucleon and pion-delta excited states. In two-point functions, these contributions are small, in accordance with general properties of the spectral weights on a torus. For the axial-current correlation function in the nucleon, the sign of excited-state contributions suggests overestimation of the nucleon axial charge. Thus contamination from pion-nucleon excited states will not likely explain the trend in lattice QCD data.
Comments:
9 pages, 5 figures, PoS.cls. Talk given at the 8th International Workshop on Chiral Dynamics, 29 June 2015 - 03 July 2015, Pisa, Italy
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.00163 [pdf]
PoS(2016)·5 citations
05
[Submitted on 3 Aug 2015] (cross-list from hep-ph)
The observation of light nuclei at ALICE and the X(3872) conundrum
A. Esposito🇺🇸 · A.L. Guerrieri🇮🇹 · L. Maiani🇮🇹 · F. Piccinini🇮🇹 · A. Pilloni🇮🇹 · A.D. Polosa🇮🇹 · V. Riquer🇮🇹
The new data reported by ALICE on the production of light nuclei with pT < 10 GeV in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV are used to compute an order-of-magnitude estimate of the expected production cross sections of light nuclei in proton-proton collisions at high transverse momenta. We compare the hypertriton, helium-3 and deuteron production cross sections to that of X(3872), measured in prompt pp collisions by CMS. The results we find suggest a different production mechanism for the X(3872), making questionable any loosely bound molecule interpretation.
Comments:
5 pages, 2 figures. Version accepted on PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.00295 [pdf]
PRD(2015)·70 citations
06
[Submitted on 3 Aug 2015] (cross-list from nucl-ex)
Observation of Spin-Dependent Charge Symmetry Breaking in $Λ N$ Interaction: Gamma-Ray Spectroscopy of $_{Λ}^{4}$ He
T. O. Yamamoto🇯🇵 · M. Agnello🇮🇹 · Y. Akazawa🇯🇵 · N. Amano🇯🇵 · K. Aoki🇯🇵 · E. Botta🇮🇹 · N. Chiga🇯🇵 · H. Ekawa🇯🇵 · P. Evtoukhovitch🇷🇺 · A. Feliciello🇮🇹 · M. Fujita🇯🇵 · T. Gogami🇯🇵 and 42 other authors
The energy spacing between the ground-state spin doublet of $_{Λ}^{4}$ He(1 $^{+}$ ,0 $^{+}$ ) was determined to be $1406 \pm 2 \pm 2$ keV, by measuring $γ$ rays for the $1^{+} \to 0^{+}$ transition with a high efficiency germanium detector array in coincidence with the $^{4}$ He $(K^{-}, π^{-})$ $_{Λ}^{4}$ He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus $_{Λ}^{4}$ H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in $Λ N$ interaction. It is also found that the CSB effect is large in the $0^{+}$ ground state but is by one order of magnitude smaller in the $1^{+}$ excited state, demonstrating that the $Λ N$ CSB interaction has spin dependence.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1508.00376 [pdf]
PRL(2015)·142 citations
07
[Submitted on 3 Aug 2015] (cross-list from hep-ph)
Effects of TMD evolution and partonic flavor on $e^{+} e^{-}$ annihilation into hadrons
Alessandro Bacchetta🇮🇹 · Miguel G. Echevarria🇳🇱 · Piet J.G. Mulders🇳🇱 · Marco Radici🇮🇹 · Andrea Signori🇳🇱
We calculate the transverse momentum dependence in the production of two back-to-back hadrons in electron-positron annihilations at the medium/large energy scales of BES-III and BELLE experiments. We use the parameters of the transverse-momentum-dependent (TMD) fragmentation functions that were recently extracted from the semi-inclusive deep-inelastic-scattering multiplicities at low energy from HERMES. TMD evolution is applied according to different approaches and using different parameters for the nonperturbative part of the evolution kernel, thus exploring the sensitivity of our results to these different choices and to the flavor dependence of parton fragmentation functions. We discuss how experimental measurements could discriminate among the various scenarios.
Comments:
33 pages, 10 composite figures, JHEP style file
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1508.00402 [pdf]
JHEP(2015)·52 citations
08
[Submitted on 3 Aug 2015] (cross-list from hep-ph)
Coincidence charged-current neutrino-induced deuteron disintegration
O. Moreno🇺🇸 · T. W. Donnelly🇺🇸 · J. W. Van Orden🇺🇸 · W. P. Ford🇺🇸
Deuteron disintegration by charged-current neutrino (CC $ν$ ) scattering offers the possibility to determine the energy of the incident neutrino by measuring in coincidence two of the three resulting particles: a charged lepton (usually a muon) and two protons, where we show that this channel can be isolated from all other, for instance, from those with a pion in the final state. We discuss the kinematics of the process for several detection scenarios, both in terms of kinematic variables that are natural from a theoretical point of view and others that are better matched to experimental situations. The deuteron structure is obtained from a relativistic model (involving an approximation to the Bethe-Salpeter equation) as an extension of a previous, well-tested model used in deuteron electrodisintegration. We provide inclusive and coincidence (semi-inclusive) cross sections for a variety of kinematic conditions, using the plane-wave impulse approximation, introducing final-state hadronic exchange terms (plane-wave Born approximation) and final-state hadronic interactions (distorted-wave Born approximation).
Comments:
31 pages, 14 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.00492 [pdf]
PRD(2015)·8 citations
09
[Submitted on 3 Aug 2015] (cross-list from hep-ph)
Bridging Soft-Hard Transport Properties of Quark-Gluon Plasmas with CUJET3.0
Jiechen Xu🇺🇸 · Jinfeng Liao🇺🇸 · Miklos Gyulassy🇺🇸
A new model of jet quenching in nuclear collisions, CUJET3.0, is constructed by generalizing the perturbative QCD based CUJET2.0 model to include two complementary non-perturbative features of the QCD confinement cross-over phase transition near $T_{c} \approx 160$ MeV: (1) the suppression of quark and gluon degrees of freedom and (2) the emergence of chromo-magnetic monopole degrees of freedom. Such a semi-Quark-Gluon-Monopole Plasma (sQGMP) microscopic scenario is tested by comparing predictions of the leading hadron nuclear modification factors, $R_{AA}^{h} (p_{T} > 10 GeV/c, s)$ , and their azimuthal elliptic asymmetry $v_{2}^{h} (p_{T} > 10 GeV/c, s)$ with available data on $h = π, D, B$ jet fragments from nuclear collisions at RHIC( $s = 0.2$ ATeV) and LHC( $s$ =2.76 ATeV). The sQGMP model is shown to solve the long standing $R_{AA}$ vs $v_{2}$ puzzle by predicting a maximum of the jet quenching parameter field $q^(E, T) / T^{3}$ near $T_{c}$ . The consistency of jet quenching with observed bulk perfect fluidity is demonstrated by extrapolating the sQGMP $q^$ down to thermal energy $E \sim 3 T$ scales and showing that the sQGMP shear viscosity to entropy density ratio $η / s \approx T^{3} / q^$ falls close to the unitarity bound, $1/4 π$ , in the range $(1 - 2) T_{c}$ . Detailed comparisons of CUJET2.0 and CUJET3.0 reveal that the remarkably different $q^(T)$ could be consistent with the same $R_{AA}$ data and could only be distinguished by anisotropy observables. These findings demonstrate clearly the inadequacy of focusing on the jet path averaged quantity $< q^>$ as the only relevant medium property to characterize jet quenching, and point to the crucial roles of other essential factors, such as the chromo electric and magnetic composites of the plasma, the screening masses and the running couplings at multiple scales that all strongly influence jet energy loss.
Comments:
50 pages, 14 figures; v3: typos corrected, new references and discussions included; published in JHEP
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1508.00552 [pdf]
JHEP(2016)·162 citations

Affiliations

first authorsco-authorsvia INSPIRE

Excited-state contamination in nucleon correlators from chiral perturbation theory

The observation of light nuclei at ALICE and the X(3872) conundrum

Observation of Spin-Dependent Charge Symmetry Breaking in ΛN Interaction: Gamma-Ray Spectroscopy of Λ4​He

Effects of TMD evolution and partonic flavor on e+e− annihilation into hadrons

Coincidence charged-current neutrino-induced deuteron disintegration

Bridging Soft-Hard Transport Properties of Quark-Gluon Plasmas with CUJET3.0

Affiliations

Observation of Spin-Dependent Charge Symmetry Breaking in $Λ N$ Interaction: Gamma-Ray Spectroscopy of $_{Λ}^{4}$ He

Effects of TMD evolution and partonic flavor on $e^{+} e^{-}$ annihilation into hadrons