Tue·Feb 14, 2017Tuesday·February 14, 2017

1. 01*

   Measurement of the stellar ${}^{58}$Ni$(n,\gamma {)}^{59}$Ni cross section with AMS

   Peter Ludwig · Georg Rugel · Iris Dillmann🇨🇦 · Thomas Faestermann🇩🇪 · Leticia Fimiani · Karin Hain · Gunther Korschinek🇩🇪 · Johannes Lachner🇦🇹 · Mikhail Poutivtsev · Klaus Knie · Michael Heil · Franz Käppeler🇩🇪 · Anton Wallner🇦🇺

   The ${}^{58}$Ni$(n,\gamma {)}^{59}$Ni cross section was measured with a combination of the activation technique and accelerator mass spectrometry (AMS). The neutron activations were performed at the Karlsruhe 3.7 MV Van de Graaff accelerator using the quasi-stellar neutron spectrum at $kT=25$ keV produced by the ${}^7$Li($p,n$)${}^7$Be reaction. The subsequent AMS measurements were carried out at the 14 MV tandem accelerator of the Maier-Leibnitz-Laboratory in Garching using the Gas-filled Analyzing Magnet System (GAMS). Three individual samples were measured, yielding a Maxwellian-averaged cross section at $kT=30$ keV of $⟨\sigma {⟩}_{30\text{keV}}$= 30.4 (23)${}^{syst}$(9)${}^{stat}$ mbarn. This value is slightly lower than two recently published measurements using the time-of-flight (TOF) method, but agrees within the uncertainties. Our new results also resolve the large discrepancy between older TOF measurements and our previous value.

   ↳ astro-ph.SRnucl-exPRC(2017)·5 citations
2. 02*

   Non-Universal and Universal Aspects of The Large Scattering Length Limit

   Gerald A. Miller🇺🇸

   The momentum density, $n(k)$ of interacting many-body Fermionic systems is studied (for $k>k_F)$ using examples of several well-known two-body interaction models. This work shows that $n(k)$ can not be approximated by a zero-range model for momenta $k$ greater than about $1/(a{r}_e^2{)}^{1/3}$, where $a$ is the scattering length, and $r_e$ the effective range. However, if the scattering length is large and one includes the effects of a fixed value of $r_e\ne 0$, $n(k)$ is universal for momenta $k$ up to about $2/r_e$. An accurate relation between the energy of a two component Fermi-gas and an integral involving the density is derived. The short separation distance, $s$, behavior of the pair density is shown to vary as $s^6$.

   ↳ nucl-thcond-mat.quant-gasnucl-exphysics.atm-clus+1PLB(2018)·6 citations
3. 03*

   Deep inelastic scattering as a probe of entanglement

   Dmitri E. Kharzeev🇺🇸 · Eugene M. Levin🇮🇱

   Using non-linear evolution equations of QCD, we compute the von Neumann entropy of the system of partons resolved by deep inelastic scattering at a given Bjorken $x$ and momentum transfer $q^2=-Q^2$. We interpret the result as the entropy of entanglement between the spatial region probed by deep inelastic scattering and the rest of the proton. At small $x$ the relation between the entanglement entropy $S(x)$ and the parton distribution $xG(x)$ becomes very simple: $S(x)=\ln [xG(x)]$. In this small $x$, large rapidity $Y$ regime, all partonic micro-states have equal probabilities -- the proton is composed by an exponentially large number $\exp (\Delta Y)$ of micro-states that occur with equal and exponentially small probabilities $\exp (-\Delta Y)$, where $\Delta$ is defined by $xG(x)\sim 1/x^{\Delta }$. For this equipartitioned state, the entanglement entropy is maximal -- so at small $x$, deep inelastic scattering probes a {\it maximally entangled state}. We propose the entanglement entropy as an observable that can be studied in deep inelastic scattering. This will require event-by-event measurements of hadronic final states, and would allow to study the transformation of entanglement entropy into the Boltzmann one. We estimate that the proton is represented by the maximally entangled state at $x\le 10^{-3}$; this kinematic region will be amenable to studies at the Electron Ion Collider.

   ↳ hep-phhep-exhep-thnucl-exPRD(2017)·265 citations
4. 04*

   Elliptic flow of $\varphi$-meson at intermediate $p_T$: Influence of mass versus quark number

   Subikash Choudhury🇮🇳 · Debojit Sarkar🇮🇳 · Subhasis Chattopadhyay🇮🇳

   We have studied elliptic flow ($v_2$) of $\varphi$-mesons in the framework of a multi phase transport (AMPT) model at LHC energy. In the realms of AMPT model we observe $\varphi$-mesons at intermediate transverse momentum ($p_T$) deviate from the previously observed (at RHIC) particle type grouping of $v_2$ according to the number of quark content i.e, baryons and mesons. Recent results from the ALICE Collaboration have shown that $\varphi$-meson and proton $v_2$ has a similar trend, possibly indicating that particle type grouping might be due to the mass of the particles and not the quark content. A stronger radial boost at LHC compared to RHIC seems to offer a consistent explanation to such observation. However, recalling that $\varphi$-mesons decouple from the hadronic medium before additional radial flow is build-up in the hadronic phase, similar pattern in $\varphi$-meson and proton $v_2$ may not be due to radial flow alone. Our study reveals that models incorporating $\varphi$-meson production from $K\bar{K}$ fusion in the hadronic rescattering phase also predict a comparable magnitude of $\varphi$-meson and proton $v_2$ particularly in the intermediate region of $p_T$. Whereas, $v_2$ of $\varphi$-mesons created in the partonic phase is in agreement with quark-coalescence motivated baryon-meson grouping of hadron $v_2$. This observation seems to provide a plausible alternative interpretation for the apparent mass-like behaviour of $\varphi$-meson $v_2$. We have also observed a violation of hydrodynamical mass ordering between proton and $\varphi$-meson $v_2$ further supporting that $\varphi$-mesons are negligibly affected by the collective radial flow in the hadronic phase due to the small in-medium hadronic interaction cross sections.

   ↳ nucl-thnucl-exPRC(2017)·3 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.