• Yong-Yeon Keum

      Articles written in Pramana – Journal of Physics

    • Phenomenological applications ofkTfactorization

      Yong-Yeon Keum

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      We discuss applications of the perturbative QCD approach in the exclusive non-leptonic two-bodyB-meson decays. We briefly review its ingredients and some important theoretical issues on the factorization approach. PQCD results are compatible with present experimental data for charmless B-meson decays. We predict the possibility of large direct CP asymmetry in B0 → π+π (23 +7%) and B0K+π (− 17 ± 5%). We also investigate the branching ratios, CP asymmetry and isospin symmetry breaking in radiativeB(K*/ρ)γ decays.

    • 𝐵 Physics: WHEPP-XI working group report

      Amol Dighe Anjan Giri Rupak Dutta Naveen Gaur Tim Gershon Diptimoy Ghosh Xiao-Gang He George W-S Hou Yong-Yeon Keum Bhavik Kodrani Namit Mahajan Joaquim Matias Barilang Mawlong Basudha Misra Rukmani Mohanta Gagan Mohanty Sudhir Vempati

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      We present the report of the 𝐵 physics working group of the Workshop on High Energy Physics Phenomenology (WHEPP-XI), held at the Physical Research Laboratory, Ahmedabad, in January 2010.

    • The TeV-scale cosmic ray proton and helium spectra: Contributions from the local sources

      Yong-Yeon Keum Pierre Salati

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      Recent measurements of cosmic ray proton and helium spectra show a hardening above a few hundreds of GeV. This excess is hard to understand in the framework of the conventional models of galactic cosmic ray production and propagation. Here, we propose to explain this anomaly by the presence of local sources. Cosmic ray propagation is described as a diffusion process taking place inside a two-zone magnetic halo. We calculate the proton and helium fluxes at the Earth between 50 GeV and 100 TeV. Improving over a similar analysis, we consistently derive these fluxes by taking into account both local and remote sources for which a unique injection rate is assumed. We find cosmic ray propagation parameters for which the proton and helium spectra remarkably agree with the PAMELA and CREAM measurements over four decades in energy.

    • Neutrino mass bounds from neutrinoless double beta-decays and cosmological probes

      Yong-Yeon Keum

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      We investigate the way the total mass sum of neutrinos can be constrained from the neutrinoless double beta-decay and cosmological probes with cosmic microwave background (CMBR), large-scale structures including 2dFGRS and SDSS datasets. First we discuss, in brief, the current status of neutrino mass bounds from neutrino beta decays and cosmic constraint within the flat 𝛬CMD model. In addition, we explore the interacting neutrino dark-energy model, where the evolution of neutrino masses is determined by quintessence scalar field, which is responsible for cosmic acceleration. Assuming the flatness of the Universe, the constraint we can derive from the current observation is 𝛴𝑚𝜈 < 0.87 eV at 95% confidence level, which is consistent with 𝛴𝑚𝜈 < 0.68 eV in the flat 𝛬CDM model without Lyman alpha forest data. In the presence of Lyman-𝛼 forest data, interacting dark-energy models prefer a weaker bound 𝛴𝑚𝜈 < 0.43 eV to 𝛴𝑚𝜈 < 0.17 eV (Seljark et al). Finally, we discuss the future prospect of the neutrino mass bound with weak-lensing effects.

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