Nuclear Theory·nucl-th

Wednesday·October 24, 2018

8 papers—4 primary·4 cross-listed

05
[Submitted on 23 Oct 2018] (cross-list from nucl-ex)
Simulation studies of $R_{2} (Δ η, Δ φ)$ and $P_{2} (Δ η, Δ φ)$ correlation functions in pp collisions with the PYTHIA and HERWIG models
Baidyanath Sahoo🇮🇳 · Basanta Kumar Nandi🇮🇳 · Prabhat Pujahari🇮🇳 · Sumit Basu🇺🇸 · Claude Pruneau🇺🇸
We report studies of charge-independent (CI) and charge-dependent (CD) two-particle differential-number correlation functions, $R_{2} (Δ η, Δ φ)$ , and transverse momentum ( $p_{T}$ ) correlation functions, $P_{2} (Δ η, Δ φ)$ , of charged particles in $s$ = 2.76 TeV pp collisions with the PYTHIA and HERWIG models. Model predictions are presented for inclusive charged hadrons ( $h^{\pm}$ ), as well as pions ( $π^{\pm}$ ), kaons (K $^{\pm}$ ), and (anti-)protons ( $p ˉ$ /p) in the ranges $0.2 < p_{T} \leq 2.0 GeV / c$ , $2.0 < p_{T} \leq 5.0 GeV / c$ , and $5.0 < p_{T} \leq 30.0 GeV / c$ , with full azimuthal coverage in the range $∣ η ∣ < 1.0$ . We compare the model predictions for the strength and shape of the $R_{2}$ and $P_{2}$ correlators as these pertain to recent measurements by the ALICE collaboration. The $R_{2}$ and $P_{2}$ correlation functions estimated with PYTHIA and HERWIG exhibit qualitatively similar near-side and away-side correlation structures but feature important differences. Our analysis indicates that comparative studies of $R_{2}$ and $P_{2}$ correlation functions would provide valuable insight towards the understanding of particle production in pp collisions, and by extension, should also be useful in studies of heavy-ion collisions. Comparison of the $Δ η$ dependence of $R_{2}$ and $P_{2}$ could contribute, in particular, to a better understanding and modeling of the angular ordering of particles produced by hadronization in jets, as well as a better description of jet fragmentation functions of identified species at low momentum fraction $(z)$ .
Comments:
22 pages, 24 captioned figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1810.09747 [pdf]
PRC(2019)·13 citations
06
[Submitted on 23 Oct 2018] (cross-list from hep-ph)
Chiralspin symmetry and its implications for QCD
L. Ya. Glozman🇦🇹
In a local gauge-invariant theory with massless Dirac fermions a symmetry of the Lorentz-invariant fermion charge is larger than a symmetry of the Lagrangian as a whole. While the Dirac Lagrangian exhibits only a chiral symmetry, the fermion charge operator is invariant under a larger symmetry group, SU(2N_F), that includes chiral transformations as well as SU(2)_{CS} chiralspin transformations that mix the right- and left-handed components of fermions. Consequently a symmetry of the electric interaction, that is driven by the charge density, is larger than a symmetry of the magnetic interaction and of the kinetic term. This allows to separate in some situations electric and magnetic contributions. In particutar, in QCD the chromo-magnetic interaction contributes only to the near-zero modes of the Dirac operator, while confining chromo-electric interaction contributes to all modes. At high temperatures, above the chiral restoration crossover, QCD exhibits approximate SU(2)_{CS} and SU(2N_F) symmetries that are incompatible with free deconfined quarks. Consequently elementary objects in QCD in this regime are quarks with a definite chirality bound by the chromo-electric field, without the chromo-magnetic effects. In this regime QCD can be described as a stringy fluid.
Comments:
11 pages; Talk given at 7th International Conference on New Frontiers in Physics (ICNFP 2018), Crete, 4-12 July 2018; Symposium "Quantum Chromodynamics and its Symmetries", Oberwoelz, Austria, 9-15 September 2018; final version; to appear in Universe
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1810.09886 [pdf]
Universe(2019)·6 citations
07
[Submitted on 23 Oct 2018] (cross-list from hep-ph)
Hyperon resonances coupled to pseudoscalar- and vector-baryon channels
K. P. Khemchandani🇧🇷 · A. Martínez Torres🇧🇷 · J. A. Oller🇪🇸
We study hyperon resonances by solving coupled channel scattering equations. The coupled systems include pseudoscalar- and vector-baryon channels. The parameters of the model are restricted by making a $χ^{2}$ -fit to the cross section data on processes: $K^{-} p \to K^{-} p$ , $K^{-} p \to K ˉ^{0} n$ , $K^{-} p \to η Λ$ , $K^{-} p \to π^{0} Λ$ , $K^{-} p \to π^{0} Σ^{0}$ , $K^{-} p \to π^{\pm} Σ^{\mp}$ . Data on the energy level shift and width of the $1 s$ state of the kaonic hydrogen, as well as some cross-section ratios near the threshold are also considered in the fit. Two types of fits are found as a result. In both cases, the properties of $Λ (1405)$ are well reproduced. In addition to this, a $Σ$ state is also found with mass around 1400 MeV. Cross sections, obtained with one of the two fits, are found to stay close to the data at energies away from the thresholds too, and as a result resonances with higher masses have also been studied.
Comments:
Published version in Physics. Rev. C
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1810.09990 [pdf]
PRC(2019)·40 citations
08
[Submitted on 23 Oct 2018] (cross-list from hep-lat)
Controlling Excited-State Contributions with Distillation in Lattice QCD Calculations of Nucleon Isovector Charges $g_{S}^{u - d}$ , $g_{A}^{u - d}$ , $g_{T}^{u - d}$
Colin Egerer🇺🇸 · David Richards🇺🇸 · Frank Winter🇺🇸
We investigate the application of the distillation smearing approach, and the use of the variational method with an extended basis of operators facilitated by this approach, on the calculation of the nucleon isovector charges $g_{S}^{u - d}$ , $g_{A}^{u - d}$ , and $g_{T}^{u - d}$ . We find that the better sampling of the lattice enabled through the use of distillation yields a substantial reduction in the statistical uncertainty in comparison with the use of alternative smearing methods, and furthermore, appears to offer better control over the contribution of excited-states compared to use of a single, local interpolating operator. The additional benefit arising through the use of the variational method in the distillation approach is less dramatic, but nevertheless significant given that it requires no additional Dirac inversions.
Comments:
17 pages, 17 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1810.09991 [pdf]
PRD(2019)·27 citations

Affiliations

first authorsco-authorsvia INSPIRE

Simulation studies of R2​(Δη,Δφ) and P2​(Δη,Δφ) correlation functions in pp collisions with the PYTHIA and HERWIG models

Chiralspin symmetry and its implications for QCD

Hyperon resonances coupled to pseudoscalar- and vector-baryon channels

Controlling Excited-State Contributions with Distillation in Lattice QCD Calculations of Nucleon Isovector Charges gSu−d​, gAu−d​, gTu−d​

Affiliations

Simulation studies of $R_{2} (Δ η, Δ φ)$ and $P_{2} (Δ η, Δ φ)$ correlation functions in pp collisions with the PYTHIA and HERWIG models

Controlling Excited-State Contributions with Distillation in Lattice QCD Calculations of Nucleon Isovector Charges $g_{S}^{u - d}$ , $g_{A}^{u - d}$ , $g_{T}^{u - d}$