Tue·Apr 28, 2020Tuesday·April 28, 2020

1. 01*

   Modified Structure of Protons and Neutrons in Correlated Pairs

   B. Schmookler · M. Duer · A. Schmidt · O. Hen · S. Gilad · E. Piasetzky · M. Strikman · L.B. Weinstein · The CLAS Collaboration

   The atomic nucleus is made of protons and neutrons (nucleons), that are themselves composed of quarks and gluons. Understanding how the quark-gluon structure of a nucleon bound in an atomic nucleus is modified by the surrounding nucleons is an outstanding challenge. Although evidence for such modification, known as the EMC effect, was first observed over 35 years ago, there is still no generally accepted explanation of its cause. Recent observations suggest that the EMC effect is related to close-proximity Short Range Correlated (SRC) nucleon pairs in nuclei. Here we report the first simultaneous, high-precision, measurements of the EMC effect and SRC abundances. We show that the EMC data can be explained by a universal modification of the structure of nucleons in neutron-proton (np) SRC pairs and present the first data-driven extraction of this universal modification function. This implies that, in heavier nuclei with many more neutrons than protons, each proton is more likely than each neutron to belong to an SRC pair and hence to have its quark structure distorted.

   nucl-exhep-phnucl-thNature(2019)·198 citations
2. 02*

   Automatic classification of nuclear physics data via a Constrained Evolutionary Clustering approach

   D. Dell'Aquila🇮🇹 · M. Russo

   This paper presents an automatic method for data classification in nuclear physics experiments based on evolutionary computing and vector quantization. The major novelties of our approach are the fully automatic mechanism and the use of analytical models to provide physics constraints, yielding to a fast and physically reliable classification with nearly-zero human supervision. Our method is successfully validated by using experimental data produced by stacks of semiconducting detectors. The resulting classification is highly satisfactory for all explored cases and is particularly robust to noise. The algorithm is suitable to be integrated in the online and offline analysis programs of existing large complexity detection arrays for the study of nucleus-nucleus collisions at low and intermediate energies.

   nucl-exphysics.comp-phphysics.data-anComput.Phys.Commun.(2021)·6 citations
3. 03*

   J/$\psi$ production as a function of charged-particle multiplicity in p-Pb collisions at $\sqrt{{\text{s}}_{\mathrm{NN}}}=8.16$ TeV

   ALICE Collaboration

   Inclusive J/$\psi$ yields and average transverse momenta in p-Pb collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV are measured as a function of the charged-particle pseudorapidity density with ALICE. The J/$\psi$ mesons are reconstructed at forward $(2.03<y_{\mathrm{cms}}<3.53)$ and backward ($-4.46<y_{\mathrm{cms}}<-2.96$) center-of-mass rapidity in their dimuon decay channel while the charged-particle pseudorapidity density is measured around midrapidity. The J/$\psi$ yields at forward and backward rapidity normalized to their respective average values increase with the normalized charged-particle pseudorapidity density, the former showing a weaker increase than the latter. The normalized average transverse momenta at forward and backward rapidity manifest a steady increase from low to high charged-particle pseudorapidity density with a saturation beyond the average value.

   nucl-exhep-exJHEP(2020)·33 citations
4. 04*

   Heavy Flavour measurements in Pb$-$Pb collisions with the upgraded ALICE Inner Tracking System

   D. Andreou (on behalf of the ALICE Collaboration)🇨🇭

   During the second LHC long shutdown (LS2) the Inner Tracking System (ITS) of ALICE (A Large Ion Collider Experiment) will be replaced by seven layers of CMOS Monolithic Active Pixel Sensors (MAPS). The latest innovations in silicon imaging technology allow for the construction of large, ultra-thin silicon wafers which can further improve the capabilities of the ALICE tracker. The research and development studies towards the construction of a novel vertex detector have started. The detector installation has been proposed for the third LHC long shutdown (LS3) during which the three innermost layers shall be replaced by three cylindrical layers of large curved CMOS wafers. This upgrade (ITS3) will further improve the impact parameter resolution and the tracking efficiency of low momentum particles. The innermost layer will be positioned closer to the interaction point and the material budget will be reduced down to 0.05$\%X_0$ per layer. Monte Carlo simulations of a simplified ITS3 geometry within the ITS2 design indicate an improvement in the impact parameter resolution and the tracking efficiency, which are of crucial importance for measurements of heavy-flavour hadrons. This contribution shows the improved performance for the example of the ${\Lambda }_{\mathrm{b}}$, for which the significance of its measurement is extracted based on these MC simulations. A significant improvement by almost a factor of three in the low momentum region compared to the ITS2 is observed.

   nucl-exhep-exActa Phys.Polon.Supp.(2021)·1 citation
5. 05*

   Threshold Resummation for Hadron Production in the Small-$x$ Region

   Hao-Yu Liu🇨🇳 · Zhong-Bo Kang🇺🇸 · Xiaohui Liu🇨🇳

   We study the single hadron inclusive production in the forward rapidity region in proton-nucleus collisions. We find the long-standing negative cross section at next-to-leading-order (NLO) is driven by the large negative threshold logarithmic contributions. We established a factorization theorem for resumming these logarithms with systematically improvable accuracy within the color glass condensate formalism. We demonstrate how the threshold leading logarithmic accuracy can be realized by a suitable scale choice in the NLO results. The NLO spectrums with the threshold logarithms resummed remain positive and impressive agreements with experimental data are observed.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2020)·38 citations
6. 06*

   Decoding the QCD critical behaviour in A+A collisions

   Nikolaos G. Antoniou🇬🇷 · Nikolaos Davis🇵🇱 · Fotios K. Diakonos🇬🇷 · Georgios Doultsinos🇬🇷 · Nikolaos Kalntis🇬🇷 · Alexandros Kanargias🇬🇷 · Athanasios S. Kapoyannis🇬🇷 · Vitalii Ozvenchuk🇵🇱 · Costas N. Papanicolas🇬🇷 · Andrzej Rybicki🇵🇱 · Efstathios Stiliaris🇬🇷

   In a systematic search for the QCD critical point in nuclear collisions, at the CERN SPS, it was found that intermittency measurements in the freeze-out state of central Si+Si collisions, at the maximum SPS energy, provide us with an indication of sizeable critical fluctuations. Also, rather recently, a weaker effect was traced in preliminary data of the Ar+Sc reaction for 10-20% most central collisions at (approximately) the same energy. However, the uncertainties in the analysis and the limitations of the experimental event statistics make the interpretation of the above measurements (NA49, NA61/SHINE) rather inconclusive, inviting for a further, phenomenological investigation with complementary tools and theoretical ideas. To this end, in the present work, we employ intermittency techniques within a model-independent analysis scheme (AMIAS), a novel method from Data Science [arXiv:1205.6505], in order to produce unbiased results for the parameters of the power-laws and in particular for the associated power-law exponent (intermittency index) ${\varphi }_2$. Using data-sets at different peripheralities, we also study the dependence of the ${\varphi }_2$-value on the number of wounded nucleons, in order to uncover the approach to the critical point. With these findings and the help of Ising-QCD partition function, the interpretation of SPS intermittency measurements and their links to the critical region, are discussed.

   ↳ nucl-thhep-phnucl-exNPA(2020)·10 citations
7. 07*

   A QCD analysis of near-threshold quarkonium leptoproduction at large photon virtualities

   Renaud Boussarie🇺🇸 · Yoshitaka Hatta🇺🇸

   We propose a novel approach to compute the cross section of near-threshold $J/\psi$ and ${\rm Y}$ production in electron-proton scattering at large photon virtualities $Q^2$ based on an operator product expansion. We show that the process can be used to extract the gluon part of the D-term gravitational form factor of the proton. At the subleading level, it is also sensitive to the trace anomaly effect of QCD.

   ↳ hep-phnucl-exPRD(2020)·51 citations
8. 08*

   Parametric unfolding. Method and restrictions

   Nikolay Gagunashvili🇮🇸

   Parametric unfolding of a true distribution distorted due to finite resolution and limited efficiency for the registration of individual events is discussed. Details of the computational algorithm of the unfolding procedure are presented.

   ↳ physics.data-anastro-ph.IMhep-exnucl-ex+1Eur.Phys.J.Plus(2020)·1 citation
9. 09*

   A technique for the study of (p,n) reactions with unstable isotopes at energies relevant to astrophysics

   P. Gastis · G. Perdikakis🇺🇸 · G.P.A. Berg · A.C. Dombos🇺🇸 · A. Estrade🇺🇸 · A. Falduto · M. Horoi🇺🇸 · S.N. Liddick🇺🇸 · S. Lipschutz🇺🇸 · S. Lyons🇺🇸 · F. Montes🇺🇸 · A. Palmisano and 11 other authors

   We have developed and tested an experimental technique for the measurement of low-energy (p,n) reactions in inverse kinematics relevant to nuclear astrophysics. The proposed setup is located at the ReA3 facility at the National Superconducting Cyclotron Laboratory. In the current approach, we operate the beam-transport line in ReA3 as a recoil separator while tagging the outgoing neutrons from the (p,n) reactions with the low-energy neutron detector array (LENDA). The developed technique was verified by using the ${}^{40}$Ar(p,n)${}^{40}$K reaction as a probe. The results of the proof-of-principle experiment with the ${}^{40}$Ar beam show that cross-section measurements within an uncertainty of $\sim$25\% are feasible with count rates up to 7 counts/mb/pnA/s. In this article, we give a detailed description of the experimental setup, and present the analysis method and results from the test experiment. Future plans on using the technique in experiments with the separator for capture reactions (SECAR) that is currently being commissioned are also discussed.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2021)·5 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.