Fri·Sep 22, 2017Friday·September 22, 2017

1. 01*

   Observation of top quark production in proton-nucleus collisions

   CMS Collaboration

   The first observation of top quark production in proton-nucleus collisions is reported using proton-lead data collected by the CMS experiment at the CERN LHC at a nucleon-nucleon center-of-mass energy of sqrt(s[NN]) = 8.16 TeV. The measurement is performed using events with exactly one isolated electron or muon and at least four jets. The data sample corresponds to an integrated luminosity of 174 inverse nanobarns. The significance of the tt-bar signal against the background-only hypothesis is above five standard deviations. The measured cross section is sigma[tt-bar] = 45 +/- 8 nb, consistent with predictions from perturbative quantum chromodynamics.

   nucl-exhep-exPRL(2017)·96 citations
2. 02*

   Semi-Inclusive ${\pi }_0$ target and beam-target asymmetries from 6 GeV electron scattering with CLAS

   S. Jawalkar · S. Koirala · H. Avakian · P. Bosted · K.A. Griffioen · C. Keith · S.E. Kuhn · K.P. Adhikari · S. Adhikari · D. Adikaram · Z. Akbar · M.J. Amaryan and 152 other authors

   We present precision measurements of the target and beam-target spin asymmetries from neutral pion electroproduction in deep-inelastic scattering (DIS) using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. We scattered 6-GeV, longitudinally polarized electrons off longitudinally polarized protons in a cryogenic ${}^{14}$NH${}_3$ target, and extracted double and single target spin asymmetries for $ep\to e^{\prime }{\pi }^{0}X$ in multidimensional bins in four-momentum transfer ($1.0<Q^2<3.2$ GeV${}^2$), Bjorken-$x$ ($0.12<x<0.48$), hadron energy fraction ($0.4<z<0.7$), transverse pion momentum ($0<P_T<1.0$ GeV), and azimuthal angle ${\varphi }_h$ between the lepton scattering and hadron production planes. We extracted asymmetries as a function of both $x$ and $P_T$, which provide access to transverse-momentum distributions of longitudinally polarized quarks. The double spin asymmetries depend weakly on $P_T$. The $\sin 2{\varphi }_h$ moments are zero within uncertainties, which is consistent with the expected suppression of the Collins fragmentation function. The observed $\sin {\varphi }_h$ moments suggest that quark gluon correlations are significant at large $x$.

   nucl-exhep-phPLB(2018)·18 citations
3. 03*

   Transverse-momentum-dependent Multiplicities of Charged Hadrons in Muon-Deuteron Deep Inelastic Scattering

   M. Aghasyan · R. Akhunzyanov · M.G. Alexeev · G.D. Alexeev · A. Amoroso · V. Andrieux · N.V. Anfimov · V. Anosov · A. Antoshkin · K. Augsten · W. Augustyniak · A. Austregesilo and 219 other authors

   A semi-inclusive measurement of charged hadron multiplicities in deep inelastic muon scattering off an isoscalar target was performed using data collected by the COMPASS Collaboration at CERN. The following kinematic domain is covered by the data: photon virtuality $Q^2>1$ (GeV/$c$)${}^2$, invariant mass of the hadronic system $W>5$ GeV/$c^2$, Bjorken scaling variable in the range $0.003<x<0.4$, fraction of the virtual photon energy carried by the hadron in the range $0.2<z<0.8$, square of the hadron transverse momentum with respect to the virtual photon direction in the range 0.02 (GeV/$c{)}^2<P_{\mathrm{hT}}^2<3$ (GeV/$c$)${}^2$. The multiplicities are presented as a function of $P_{\mathrm{hT}}^2$ in three-dimensional bins of $x$, $Q^2$, $z$ and compared to previous semi-inclusive measurements. We explore the small-$P_{\mathrm{hT}}^2$ region, i.e. $P_{\mathrm{hT}}^2<1$ (GeV/$c$)${}^2$, where hadron transverse momenta are expected to arise from non-perturbative effects, and also the domain of larger $P_{\mathrm{hT}}^2$, where contributions from higher-order perturbative QCD are expected to dominate. The multiplicities are fitted using a single-exponential function at small $P_{\mathrm{hT}}^2$ to study the dependence of the average transverse momentum $⟨P_{\mathrm{hT}}^2⟩$ on $x$, $Q^2$ and $z$. The power-law behaviour of the multiplicities at large $P_{\mathrm{hT}}^2$ is investigated using various functional forms. The fits describe the data reasonably well over the full measured range.

   ↳ hep-exnucl-exPRD(2018)·88 citations
4. 04*

   A new "3D Calorimetry" of hot nuclei

   E. Vient🇫🇷 · L. Manduci🇫🇷 · E. Legouée🇫🇷 · L. Augey🇫🇷 · E. Bonnet🇫🇷 · B. Borderie🇫🇷 · R. Bougault🇫🇷 · A. Chbihi🇫🇷 · D. Dell'Aquila🇫🇷 · Q. Fable🇫🇷 · L. Francalanza🇮🇹 · J.D. Frankland🇫🇷 and 18 other authors

   In the domain of Fermi energy, it is extremely complex to isolate experimentally fragments and particles issued from the cooling of a hot nucleus produced during a heavy ion collision. This paper presents a new method to characterize more precisely hot Quasi-Projectiles. It tries to take into account as accurately as possible the distortions generated by all the other potential participants in the nuclear reaction. It is quantitatively shown that this method is a major improvement respect to classic calorimetries used with a 4$\pi$ detector array. By detailing and deconvolving the different steps of the reconstitution of the hot nucleus, this study shows also the respective role played by the experimental device and the event selection criteria on the quality of the determination of QP characteristics.

   ↳ physics.data-annucl-exPRC(2018)·6 citations
5. 05*

   New low-$Q^2$ measurements of the ${\gamma }^{\ast }N\to \Delta (1232)$ Coulomb quadrupole form factor, pion cloud parametrizations and Siegert's theorem

   G. Ramalho🇧🇷

   The novel measurements of the ${\gamma }^{\ast }N\to \Delta (1232)$ Coulomb quadrupole form factor in the range $Q^2=0.04$--0.13 GeV${}^2$ changed the trend of the previous data. With the new data the electric and Coulomb form factors are both in remarkable agreement with estimates of the pion cloud contributions to the quadrupole form factors at low $Q^2$. The pion cloud contributions to the electric and Coulomb form factors can be parametrized by the relations $G_E\propto G_{En}/\left(1+\frac{Q^2}{2M_{\Delta }(M_{\Delta }-M)}\right)$ and $G_C\propto G_{En}$, where $G_{En}$ is the neutron electric form factor, and $M$, $M_{\Delta }$ are the nucleon and $\Delta$ masses, respectively. Those parametrizations are in full agreement with Siegert's theorem, which states that $G_E=\frac{M_{\Delta }-M}{2M_{\Delta }}{G}_C$ at the pseudothreshold, when $Q^2=-(M_{\Delta }-M{)}^2$, and improve previous parametrizations. Also a small valence quark component estimated by a covariant quark model contributes to this agreement. The combination of the new data with the new parametrization for $G_E$ concludes an intense period of studying the ${\gamma }^{\ast }N\to \Delta (1232)$ quadrupole form factors at low $Q^2$, with the agreement between theory and data.

   ↳ hep-phhep-exhep-latnucl-ex+1EPJA(2018)·22 citations
6. 06*

   Defective fission correlation data from the 2E-2v method

   Kaj Jansson🇸🇪 · Ali Al-Adili · Erik Andersson Sundén · Stephan Pomp🇸🇪 · Alf Göök · Stephan Oberstedt

   The double-energy double-velocity ($2E$-$2v$) method allows assessing fission-fragment mass yields prior to and after prompt neutron emission with high resolution. It is, therefore, considered as a complementary technique to assess average prompt neutron multiplicity as a function of fragment properties. We have studied the intrinsic features of the $2E$-$2v$ method by means of event-wise generated fission-fragment data and found severe short-comings in the method itself as well as in some common practice of application. We find that the $2E$-$2v$ method leads to large deviations in the correlation between the prompt neutron multiplicity and pre-neutron mass, which deforms and exaggerates the so called `sawtooth' shape of $\bar{\nu }(A)$. We have identified the treatment of prompt neutron emission from the fragments as the origin of the problem. The intrinsic nature of this deficiency, risk to render $2E$-$2v$ experiments much less interesting. We suggest a method to correct the $2E$-$2v$ data, and recommend applying this method to previous data acquired in $2E$-$2v$ experiments, as well.

   ↳ physics.ins-detnucl-ex0 citations
7. 07*

   The SPEDE spectrometer

   P. Papadakis🇫🇮 · D.M. Cox🇫🇮 · G.G. O'Neill🇬🇧 · M.J.G. Borge🇨🇭 · P.A. Butler🇬🇧 · L.P. Gaffney🇨🇭 · P.T. Greenlees🇫🇮 · R.-D. Herzberg🇬🇧 · A. Illana🇧🇪 · D.T. Joss🇬🇧 · J. Konki🇫🇮 · T. Kröll🇩🇪 and 9 other authors

   The electron spectrometer, SPEDE, has been developed and will be employed in conjunction with the Miniball spectrometer at the HIE-ISOLDE facility, CERN. SPEDE allows for direct measurement of internal conversion electrons emitted in-flight, without employing magnetic fields to transport or momentum filter the electrons. Together with the Miniball spectrometer, it enables simultaneous observation of {\gamma} rays and conversion electrons in Coulomb-excitation experiments using radioactive ion beams.

   ↳ physics.ins-detnucl-exEPJA(2018)·15 citations
8. 08*

   What makes the peak structure of the $\Lambda p$ invariant-mass spectrum in the $K^{-}{}^3\mathrm{He}\to \Lambda pn$ reaction?

   Takayasu Sekihara (JAEA, Ibaraki)🇯🇵 · Eulogio Oset (Valencia U. & Valencia U., IFIC)🇪🇸 · Angels Ramos (Barcelona U., ECM & ICC, Barcelona U.)🇪🇸

   Recently a peak structure was observed near the $K^{-}pp$ threshold in the in-flight ${}^3\mathrm{He}(K^{-},\Lambda p)n$ reaction of the E15 experiment at J-PARC, which could be a signal of a $\bar{K}NN$ bound state. In order to investigate what is the origin of this peak, we calculate the cross section of this reaction, in particular based on the scenario that the $\bar{K}NN$ bound state is indeed generated and decays into $\Lambda p$. We find that the numerical result of the $\Lambda p$ invariant-mass spectrum in the $\bar{K}NN$ bound scenario is consistent with the J-PARC E15 data.

   ↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2017)·2 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.