Mon·Apr 27, 2015Monday·April 27, 2015

1. 01*

   A compression algorithm for the combination of PDF sets

   Stefano Carrazza🇮🇹 · Jose I. Latorre🇪🇸 · Juan Rojo🇬🇧 · Graeme Watt🇬🇧

   The current PDF4LHC recommendation to estimate uncertainties due to parton distribution functions (PDFs) in theoretical predictions for LHC processes involves the combination of separate predictions computed using PDF sets from different groups, each of which comprises a relatively large number of either Hessian eigenvectors or Monte Carlo (MC) replicas. While many fixed-order and parton shower programs allow the evaluation of PDF uncertainties for a single PDF set at no additional CPU cost, this feature is not universal, and moreover the a posteriori combination of the predictions using at least three different PDF sets is still required. In this work, we present a strategy for the statistical combination of individual PDF sets, based on the MC representation of Hessian sets, followed by a compression algorithm for the reduction of the number of MC replicas. We illustrate our strategy with the combination and compression of the recent NNPDF3.0, CT14 and MMHT14 NNLO PDF sets. The resulting Compressed Monte Carlo PDF (CMC-PDF) sets are validated at the level of parton luminosities and LHC inclusive cross-sections and differential distributions. We determine that around 100 replicas provide an adequate representation of the probability distribution for the original combined PDF set, suitable for general applications to LHC phenomenology.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2015)·108 citations
2. 02*

   Effect of in-medium parameters of rho meson in its photoproduction reactions on nuclei

   Swapan Das🇮🇳

   There exist model calculations showing the modification of the hadronic parameters of $\rho$ meson in the nuclear environment. From these parameters, we extract the $\rho$ meson nucleus optical potential and show the medium effect due to this potential on the $\rho$ meson mass distribution spectra in the photonuclear reaction. The calculated results reproduced reasonably the measured $e^{+}{e}^{-}$ invariant mass, i.e., $\rho$ meson mass, distribution spectra in the $(\gamma ,{\rho }^0\to e^{+}{e}^{-})$ reaction on nuclei.

   ↳ nucl-thnucl-exPhys.Atom.Nucl.(2015)·2 citations
3. 03*

   CMS physics highlights in the LHC Run 1

   David d'Enterria (for the CMS Collaboration)🇨🇭

   The main physics results obtained by the CMS experiment during the first three years of operation of the CERN Large Hadron Collider (2010--2013, aka. Run 1) are summarized. The advances in our understanding of the fundamental particles and their interactions are succinctly reviewed under the following physics topics: (i) Quantum Chromodynamics, (ii) Quark Gluon Plasma, (iii) Electroweak interaction, (iv) Top quark, (v) Higgs boson, (vi) Flavour, (vii) Supersymmetry, (viii) Dark Matter, and (ix) other searches of physics beyond the Standard Model.

   ↳ hep-exhep-phnucl-exnucl-thPoS(2015)·5 citations
4. 04*

   Double-quarkonium production at a fixed-target experiment at the LHC (AFTER@LHC)

   Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇨🇭

   We present predictions for double-quarkonium production in the kinematical region relevant for the proposed fixed-target experiment using the LHC beams (dubbed as AFTER@LHC). These include all spin-triplet S -wave charmonium and bottomonium pairs, i.e. Psi(n_1S) + Psi(n_2S), Psi(n_1S) + Upsilon(m_1S) and Upsilon(m_1S) + Upsilon(m_2S ) with n_1,n_2 = 1,2 and m_1,m_2 = 1,2,3. We calculate the contributions from double-parton scatterings and single-parton scatterings. With an integrated luminosity of 20 fb-1 to be collected at AFTER@LHC, we find that the yields for double-charmonium production are large enough for differential distribution measurements. We discuss some differential distributions for J/Psi + J/Psi production, which can help to study the physics of double-parton and single-parton scatterings in a new energy range and which might also be sensitive to double intrinsic c-bar(c) coalescence at large negative Feynman x.

   ↳ hep-phhep-exnucl-exnucl-thNPB(2015)·68 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.