Mon·Aug 24, 2015Monday·August 24, 2015

1. 01*

   Coherent $\psi$(2S) photo-production in ultra-peripheral Pb-Pb collisions at ${\sqrt{s}}_{\mathrm{NN}}$ = 2.76 TeV

   ALICE Collaboration

   We have has performed the first measurement of the coherent $\psi$(2S) photo-production cross section in ultra-peripheral Pb-Pb collisions at the LHC. This charmonium excited state is reconstructed via the $\psi$(2S) $\to l^{+}{l}^{-}$ and $\psi$(2S) $\to$ J/$\psi {\pi }^{+}{\pi }^{-}$ decays, where the J/$\psi$ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 $\mu {\mathrm{b}}^{-1}$. The cross section for coherent $\psi$(2S) production in the rapidity interval $-0.9<y<0.9$ is $\mathrm{d}{\sigma }_{\psi (2S)}^{\mathrm{coh}}/\mathrm{d}y=0.83\pm 0.19(\mathrm{stat}+\mathrm{syst})$ mb. The $\psi$(2S) to J/$\psi$ coherent cross section ratio is $0.34_{-0.07}^{+0.08}(\mathrm{stat}+\mathrm{syst})$. The obtained results are compared to predictions from theoretical models.

   nucl-exhep-exPLB(2015)·71 citations
2. 02*

   Strong interaction studies with kaonic atoms

   J. Marton🇦🇹 · M. Bazzi🇮🇹 · G. Beer🇨🇦 · C. Berucci🇦🇹 · D. Bosnar🇭🇷 · A.M. Bragadireanu🇷🇴 · M. Cargnelli🇦🇹 · A. Clozza🇮🇹 · C. Curceanu🇮🇹 · A. d'Uffizi🇮🇹 · C. Fiorini🇮🇹 · F. Ghio🇮🇹 and 21 other authors

   The strong interaction of antikaons (K-) with nucleons and nuclei in the low energy regime represents an active research field connected intrinsically with few-body physics. There are important open questions like the question of antikaon nuclear bound states - the prototype system being K-pp. A unique and rather direct experimental access to the antikaon-nucleon scattering lengths is provided by precision X-ray spectroscopy of transitions in low-lying states of light kaonic atoms like kaonic hydrogen isotopes. In the SIDDHARTA experiment at the electron-positron collider DA?NE of LNF-INFN we measured the most precise values of the strong interaction observables, i.e. the strong interaction on the 1s ground state of the electromagnetically bound K-p atom leading to a hadronic shift and a hadronic broadening of the 1s state. The SIDDHARTA result triggered new theoretical work which achieved major progress in the understanding of the low-energy strong interaction with strangeness. Antikaon-nucleon scattering lengths have been calculated constrained by the SIDDHARTA data on kaonic hydrogen. For the extraction of the isospin-dependent scattering lengths a measurement of the hadronic shift and width of kaonic deuterium is necessary. Therefore, new X-ray studies with the focus on kaonic deuterium are in preparation (SIDDHARTA2). Many improvements in the experimental setup will allow to measure kaonic deuterium which is challenging due to the anticipated low X-ray yield. Especially important are the data on the X-ray yields of kaonic deuterium extracted from a exploratory experiment within SIDDHARTA.

   nucl-ex0 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.