Nuclear Theory·nucl-th

Monday·January 8, 2018

18 papers—11 primary·7 cross-listed

12
Colored Dark Matter
Valerio De Luca🇮🇹 · Andrea Mitridate🇮🇹 · Michele Redi🇮🇹 · Juri Smirnov🇮🇹 · Alessandro Strumia🇮🇹
We explore the possibility that Dark Matter is the lightest hadron made of two stable color octet Dirac fermions $Q$ . The cosmological DM abundance is reproduced for $M_{Q} \approx 12.5$ TeV, compatibly with direct searches (the Rayleigh cross section, suppressed by $1/ M_{Q}^{6}$ , is close to present bounds), indirect searches (enhanced by $Q Q + Q ˉ Q ˉ \to Q Q ˉ + Q Q ˉ$ recombination), and with collider searches (where $Q$ manifests as tracks, pair produced via QCD). Hybrid hadrons, made of $Q$ and of SM quarks and gluons, have large QCD cross sections, and do not reach underground detectors. Their cosmological abundance is $1 0^{5}$ times smaller than DM, such that their unusual signals seem compatible with bounds. Those in the Earth and stars sank to their centers; the Earth crust and meteorites later accumulate a secondary abundance, although their present abundance depends on nuclear and geological properties that we cannot compute from first principles.
↳ hep-phastro-ph.COnucl-thPRD(2018)·117 citations
13
A remark on the sign change of the four-particle azimuthal cumulant in small systems
Adam Bzdak🇵🇱 · Guo-Liang Ma🇨🇳
The azimuthal cumulants, $c_{2} {2}$ and $c_{2} {4}$ , originating from the global conservation of transverse momentum in the presence of hydro-like elliptic flow are calculated. We observe the sign change of $c_{2} {4}$ for small number of produced particles. This is in a qualitative agreement with the recent ATLAS measurement of multi-particle azimuthal correlations with the subevent cumulant method.
↳ hep-phhep-exnucl-exnucl-thPLB(2018)·10 citations
14
Chronology of the three-body dissociation of $^{8}$ He
B. Laurent🇫🇷 · F.M. Marqués🇫🇷 · C. Angulo🇧🇪 · N.I. Ashwood🇬🇧 · M.J.G. Borge🇪🇸 · V. Bouchat🇧🇪 · W.N. Catford · N.M. Clarke🇬🇧 · N. Curtis🇬🇧 · M. Freer🇬🇧 · F. Hanappe🇧🇪 · V. Kinnard🇧🇪 and 11 other authors
The space and time configurations of the dissociation of $^{8}$ He into $^{6}$ He+ $n$ + $n$ , on C and Pb targets, have been explored simultaneously for the first time. The final-state interactions in the $n$ - $n$ and $^{6}$ He- $n$ channels are successfully described within a model that considers independent emission of neutrons from a Gaussian volume with a given lifetime. The dissociation on C target exhibits a dominant sequential decay through the ground state of $^{7}$ He, consistent with neutrons being emitted from a Gaussian volume of $r_{nn}^{rms} = 7.3 \pm 0.6$ ~fm with a $n$ - $n$ delay in the sequential channel of $1400 \pm 400$ ~fm/ $c$ , in agreement with the lifetime of $^{7}$ He. The lower-statistics data on Pb target correspond mainly to direct breakup, and are well described using the $n$ - $n$ volume measured, without any $n$ - $n$ delay. The validity of the phenomenological model used is discussed.
↳ nucl-exnucl-thJ.Phys.G(2019)·9 citations
15
$N^{*}$ Form Factors based on a Covariant Quark Model
G. Ramalho🇧🇷
We discuss the results of the covariant spectator quark model for the several $γ^{*} N \to N^{*}$ transitions, where $N$ is the nucleon and $N^{*}$ a nucleon excitation. More specifically, we present predictions for the form factors and transition amplitudes associated with the resonances $N (1440) 1/ 2^{+}$ , $N (1535) 1/ 2^{-}$ , $N (1520) 3/ 2^{-}$ , $Δ (1620) 1/ 2^{-}$ and $N (1650) 1/ 2^{-}$ . The estimates based on valence quark degrees of freedom are compared with the available data, particularly with the recent Jefferson Lab data at low and large momentum transfer ( $Q^{2}$ ). In general, the estimates are in good agreement with the empirical data for $Q^{2} > 2$ GeV $^{2}$ , with a few exceptions. The results are discussed in terms of the role of the valence quarks and the meson cloud excitations for the different resonances $N^{*}$ . We also review our results for the resonance $Δ (1232) 3/ 2^{+}$ and discuss the relevance of the pion cloud component for the magnetic dipole form factor and the electric and Coulomb quadrupole form factors.
↳ hep-phhep-exhep-latnucl-ex+1Few Body Syst.(2018)·25 citations
16
Unintegrated dipole gluon distribution at small transverse momentum
Raktim Abir🇿🇦 · Khatiza Banu🇿🇦 · Trambak Bhattacharyya🇿🇦 · Mariyah Siddiqah🇿🇦 · Nahid Vasim🇿🇦
We derive analytical results for unintegrated color dipole gluon distribution function at small transverse momentum. By Fourier transforming the $S$ -matrix for large dipoles we derive the results in the form of a series of Bells polynomials. Interestingly, when resumming the series in leading log accuracy, the results showing up striking similarity with the Sudakov form factor with role play of coupling is being done by a constant that stems from the saddle point condition along the saturation line.
↳ hep-phhep-thnucl-thPRD(2018)·9 citations
17
$ψ (2 S)$ photoproduction in high energy nuclear collisions
Baoyi Chen · Carsten Greiner🇩🇪 · Wei Shi · Wangmei Zha🇨🇳 · Pengfei Zhuang🇨🇳
We study coherent photoproduction of $ψ^{'}$ and the subsequent suppression in high energy nuclear collisions. The hot medium effect on charmonium photoproduction is controlled by the competition between the fireball size and nuclear size. When the former is smaller than the later, the photoproduction is only slightly affected by the hot medium. We calculate the yield ratio of $ψ^{'}$ to $J / ψ$ in semi-central Pb-Pb collisions at LHC energy, while the high $p_{T}$ limit is characterized by the fireball, its value in low $p_{T}$ limit can still reach the significant enhancement by photoproduction.
↳ hep-phnucl-th5 citations
18
Proton charge radius from electron scattering
Ingo Sick🇨🇭
The rms-radius $R$ of the proton charge distribution is a fundamental quantity needed for precision physics. This radius, traditionally determined from elastic electron-proton scattering via the slope of the Sachs form factor $G_{e} (q^{2})$ extrapolated to momentum transfer $q^{2}$ =0, shows a large scatter. We discuss the approaches used to analyze the e-p data, partly redo these analyses in order to identify the sources of the discrepancies, and explore alternative parameterizations. The problem lies in the model dependence of the parameterized $G (q)$ needed for the extrapolation. This shape of $G (q < q_{min})$ is closely related to the shape of the charge density $ρ (r)$ at large radii $r$ , a quantity which is ignored in most analyses. When using our {\em physics} knowledge about this large- $r$ density together with the information contained in the high- $q$ data, the model dependence of the extrapolation is reduced and different parameterizations of the pre-2010 data yield a consistent value for $R = 0.887 \pm 0.012 f m$ . This value disagrees with the more precise value $0.8409 \pm 0.0004 f m$ determined from the Lamb shift in muonic hydrogen.
↳ nucl-exnucl-thAtoms(2018)·45 citations

Affiliations

first authorsco-authorsvia INSPIRE

Colored Dark Matter

A remark on the sign change of the four-particle azimuthal cumulant in small systems

Chronology of the three-body dissociation of 8He

N∗ Form Factors based on a Covariant Quark Model

Unintegrated dipole gluon distribution at small transverse momentum

ψ(2S) photoproduction in high energy nuclear collisions

Proton charge radius from electron scattering

Affiliations

Chronology of the three-body dissociation of $^{8}$ He

$N^{*}$ Form Factors based on a Covariant Quark Model

$ψ (2 S)$ photoproduction in high energy nuclear collisions