Konkuk University

About: Konkuk University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Apoptosis. The organization has 13405 authors who have published 27027 publications receiving 506313 citations.

J/ψ and ψ (2S) production in pp collisions at √s = 7 TeV

Abstract: A measurement of the J/psi and psi(2S) production cross sections in pp collisions at sqrt(s)=7 TeV with the CMS experiment at the LHC is presented. The data sample corresponds to an integrated luminosity of 37 inverse picobarns. Using a fit to the invariant mass and decay length distributions, production cross sections have been measured separately for prompt and non-prompt charmonium states, as a function of the meson transverse momentum in several rapidity ranges. In addition, cross sections restricted to the acceptance of the CMS detector are given, which are not affected by the polarization of the charmonium states. The ratio of the differential production cross sections of the two states, where systematic uncertainties largely cancel, is also determined. The branching fraction of the inclusive B to psi(2S) X decay is extracted from the ratio of the non-prompt cross sections to be: BR(B to psi(2S) X) = (3.08 +/- 0.12(stat.+syst.) +/- 0.13(theor.) +/- 0.42(BR[PDG])) 10^-3

Interpreting the 750 GeV diphoton resonance using photon jets in hidden-valley-like models

Abstract: Motivated by the diphoton resonance recently reported by the ATLAS and CMS collaborations at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$, we interpret the resonance as a scalar boson $X(750)$ in hidden-valley-like models. The scalar boson $X$ can mix with the standard model Higgs boson and thus can be produced via gluon fusion. It then decays into a pair of very light hidden particles $Y$ of $\mathcal{O}(1\text{ }\text{ }\mathrm{GeV})$, each of which in turn decays to a pair of collimated ${\ensuremath{\pi}}^{0}$'s, and these two ${\ensuremath{\pi}}^{0}$'s decay into photons which then form photon jets. A photon jet ($\ensuremath{\gamma}$ jet) is a special feature that consists of a cluster of collinear photons from the decay of a fast moving light particle [$\mathcal{O}(1\text{ }\text{ }\mathrm{GeV})$]. Because these photons inside the photon jet are so collimated that it cannot be distinguished from a single photon, in the final state of the decay of $X(750)$ a pair of photon jets looks like a pair of single photons, which the experimentalists observed and reconstructed the 750 GeV diphoton resonance. Prospects for LHC Run-2 about other new and testable features are also discussed.