Tue·May 8, 2018Tuesday·May 8, 2018

1. 01*

   The center of mass motion of short-range correlated nucleon pairs studied via the A(e,e'pp) reaction

   E.O. Cohen · O. Hen · E. Piasetzky · L.B. Weinstein · M. Duer · A. Schmidt · I. Korover · H. Hakobyan · the CLAS Collaboration

   Short-Range Correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum (kF). A fundamental characteristic of SRC pairs is having large relative momenta as compared to kF, and smaller center-of-mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton (pp) SRC pairs in Carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the A(e,e'pp) reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to 170 MeV/c, approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states.

   nucl-exnucl-thPRL(2018)·70 citations
2. 02*

   Measurement of prompt $\psi$(2S) production cross sections in proton-lead and proton-proton collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 5.02 TeV

   CMS Collaboration

   Measurements of prompt $\psi$(2S) meson production cross sections in proton-lead (pPb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 5.02 TeV are reported. The results are based on pPb and pp data collected by the CMS experiment at the LHC, corresponding to integrated luminosities of 34.6 nb${}^{-1}$ and 28.0 pb${}^{-1}$, respectively. The nuclear modification factor $R_{\mathrm{pPb}}$ is measured for prompt $\psi$(2S) in the transverse momentum range 4 $<$ p${}_{\mathrm{T}}$ $<$ 30 GeV$/c$ and the center-of-mass rapidity range $-$2.4 $<y_{\mathrm{cm}}<$ 1.93. The results on $\psi$(2S) $R_{\mathrm{pPb}}$ are compared to the corresponding modification factor for prompt J$/\psi$ mesons. The results point to different nuclear effects at play in the production of the excited charmonium state compared to the ground state, in the region of backward rapidity and for p${}_{\mathrm{T}}$ $<$ 10 GeV$/c$.

   ↳ hep-exnucl-exPLB(2019)·59 citations
3. 03*

   Universal scaling of the pion, kaon and proton $p_{\mathrm{T}}$ spectra in Pb-Pb collisions at 2.76 TeV

   Y.Y. Wang🇨🇳 · L.W. Yang🇨🇳 · X.L. Du🇨🇳 · N. Liu🇨🇳 · L.Y. Qiao🇨🇳 · W.C. Zhang🇨🇳

   With the experimental data collected by the ALICE collaboration in Pb-Pb collisions at a center-of-mass energy per nucleon pair 2.76 TeV for six different centralities (0-5$\%$, 5-10$\%$, 10-20$\%$, 20-40$\%$, 40-60$\%$ and 60-80$\%$), we investigate the scaling property of the pion, kaon and proton transverse momentum ($p_{\mathrm{T}}$) spectra at these centralities. We show that in the low $p_{\mathrm{T}}$ region with $p_{\mathrm{T}}\le$ 2.75 (3.10 and 2.35) GeV/c the pion (kaon and proton) spectra exhibit a scaling behaviour independent of the centrality of the collisions. This scaling behaviour arises when these spectra are presented in terms of a suitable variable, $z=p_{\mathrm{T}}/K$. The scaling parameter $K$ is determined by the quality factor method and is parameterized by $a⟨N_{\mathrm{part}}{⟩}^b$, where $⟨N_{\mathrm{part}}⟩$ is the average value of the number of participating nucleons, $a$ and $b$ are free parameters, $b$ characterizes the rate at which $\text{ln}K$ changes with $\text{ln}⟨N_{\mathrm{part}}⟩$. The values of $b$ for pions and kaons are consistent within uncertainties, while they are smaller than that for protons. In the high $p_{\mathrm{T}}$ region, due to the suppression of the spectra, a violation of the proposed scaling is observed going from central to peripheral collisions. The more peripheral the collisions are, the more clearly violated the proposed scaling becomes. In the framework of the colour string percolation model, we argue that the pions, kaons and protons originate from the fragmentation of clusters which are formed by strings overlapping and the cluster's fragmentation functions are different for different hadrons. The scaling behaviour of the pion, kaon and proton spectra in the low $p_{\mathrm{T}}$ region can be simultaneously explained by the colour string percolation model in a qualitative way.

   ↳ nucl-thnucl-exNPA(2018)·3 citations
4. 04*

   Nonperturbative transverse-momentum-dependent effects in dihadron and direct photon-hadron angular correlations in $p+p$ collisions at $\sqrt{s}=200$ GeV

   C. Aidala · Y. Akiba · M. Alfred · V. Andrieux · N. Apadula · H. Asano · B. Azmoun · V. Babintsev · A. Bagoly · N.S. Bandara · K.N. Barish · S. Bathe and 284 other authors

   Dihadron and isolated direct photon-hadron angular correlations are measured in $p$$+$$p$ collisions at $\sqrt{s}=200$ GeV. The correlations are sensitive to nonperturbative initial-state and final-state transverse momentum $k_T$ and $j_T$ in the azimuthal nearly back-to-back region $\Delta \varphi \sim \pi$. In this region, transverse-momentum-dependent evolution can be studied when several different hard scales are measured. To have sensitivity to small transverse momentum scales, nonperturbative momentum widths of $p_{\mathrm{out}}$, the out-of-plane transverse momentum component perpendicular to the trigger particle, are measured. These widths are used to investigate possible effects from transverse-momentum-dependent factorization breaking. When accounting for the longitudinal momentum fraction of the away-side hadron with respect to the near-side trigger particle, the widths are found to increase with the hard scale; this is qualitatively similar to the observed behavior in Drell-Yan and semi-inclusive deep-inelastic scattering interactions. The momentum widths are also studied as a function of center-of-mass energy by comparing to previous measurements at $\sqrt{s}=510$ GeV. The nonperturbative jet widths also appear to increase with $\sqrt{s}$ at a similar $x_T$, which is qualitatively consistent to similar measurements in Drell-Yan interactions. To quantify the magnitude of any transverse-momentum-dependent factorization breaking effects, calculations will need to be performed to compare to these measurements.

   ↳ hep-exnucl-exPRD(2018)·16 citations
5. 05*

   Heavy physics contributions to neutrinoless double beta decay from QCD

   A. Nicholson🇺🇸 · E. Berkowitz🇩🇪 · H. Monge-Camacho🇺🇸 · D. Brantley🇺🇸 · N. Garron🇬🇧 · C.C. Chang🇺🇸 · E. Rinaldi🇺🇸 · M.A. Clark🇺🇸 · B. Joo🇺🇸 · T. Kurth🇺🇸 · B. Tiburzi🇺🇸 · P. Vranas🇺🇸 · A. Walker-Loud🇺🇸

   Observation of neutrinoless double beta decay, a lepton number violating process that has been proposed to clarify the nature of neutrino masses, has spawned an enormous world-wide experimental effort. Relating nuclear decay rates to high-energy, beyond the Standard Model (BSM) physics requires detailed knowledge of non-perturbative QCD effects. Using lattice QCD, we compute the necessary matrix elements of short-range operators, which arise due to heavy BSM mediators, that contribute to this decay via the leading order ${\pi }^{-}\to {\pi }^{+}$ exchange diagrams. Utilizing our result and taking advantage of effective field theory methods will allow for model-independent calculations of the relevant two-nucleon decay, which may then be used as input for nuclear many-body calculations of the relevant experimental decays. Contributions from short-range operators may prove to be equally important to, or even more important than, those from long-range Majorana neutrino exchange.

   ↳ nucl-thhep-lathep-phnucl-exPRL(2018)·102 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.