Dr. Pyungwon Ko

School of Physics
Korea Institute for Advanced Study (KIAS), Korea
Email: pko.at.kias.re.kr
March 2011

I obtained my PhD from University of Chicago in 1991, with the thesis about vector meson contributions to rare kaon decays.

For a few years after my PhD, I worked on heavy quarkonium physics within nonrelativistic QCD and chiral Lagrangian technique. Some examples include the double bumps in the m_ππ spectrum in the Υ(3S)→Υ(1S)ππ, the 3π invariant mass spectrum in X(3872)→J/ψ πππ, and color octet mechanism in J/ψ productions at colliders.

From 1997, I began to study flavor and CP violation within supersymmetric models, and made a number of interesting predictions at B factories. One example is B factory observables in the minimal supersymmetric standard model (MSSM) with electroweak baryogenesis. One often argues that B factory experiments can probe new CP violating phases that might be relevant to the observed baryon number asymmetry (BAU) of the universe. On the other hand, there were no detailed study about the B meson observables that are related with the BAU. I made a number of predictions for various B meson observables that could be related with the BAU. Most interesting is the direct CP violation in B→ X_s γ, which have been searched for at B factories. Another interesting prediction I made was that B_s→μ⁺μ^- in the large tanβ region could be complementary to direct search at colliders.

Recently I have been working on cold dark matter in various setups: cold dark matter from some hidden sector (strongly or weakly interacting), and leptophilic or leptophobic dark matter motivated by direct and indirect detection experiments of dark matter. Some of them have interesting implications on Higgs phenomenology because of possibility of invisible decays of Higgs boson(s) into a pair of dark matter.

Finally I studied the top forward backward asymmetry within the dim-6 effective Lagrangian approach, and proposed a few new observables that could be useful to diagnose the underlying physics that might generate the observed asymmetry.

Do you want to know more?

• [1] Probing SUSY induced CP violations at B factories. Seungwon Baek and Pyungwon Ko, Phys.Rev.Lett.83:488-491,1999.
• [2] Contribution of b s gluon gluon through the QCD anomaly in exclusive decays B+- (eta-prime, eta) (K+-, K*+-) and B0
• (3) Color octet mechanism in gamma + p J / psi + X.
  Pyungwon Ko, Jungil Lee and H.S. Song. Phys.Rev.D54:4312-4325,1996, Erratum-ibid.D60:119902,1999.
• (4) B(d) phi K(s) CP asymmetries as an important probe of supersymmetry.
  G.L. Kane, P. Ko, Hai-bin Wang, C. Kolda, Jae-hyeon Park and Lian-Tao Wang, Phys.Rev.Lett.90:141803,2003.
• (5) Implications on SUSY breaking mediation mechanisms from observing B(s) mu+ mu- and the muon (g-2). Seungwon Baek, P. Ko and Wan Young Song. Phys.Rev.Lett.89:271801,2002.
• (6) Phenomenology of U(1)(L(mu)-L(tau)) charged dark matter at PAMELA and colliders.
  Seungwon Baek and Pyungwon Ko. JCAP 0910:011,2009.
• (7) Scale invariant extension of the standard model with strongly interacting hidden sector. Taeil Hur and Pyungwon Ko. To appear in Phys. Rev. Lett.