This analysis combine five principal decay channels in a global search for charged Higgs bosons in the decay of top quark pairs. The signature of the existence of charged Higgs boson is the difference of branching ratio in different top quark pair decay modes. For the case where the charged Higgs decay predominantly into tau leptons, there will be an enhancement in the rate of top quark pairs decaying into final states with tau leptons.
This analysis was approved as preliminary in Summer 2008 and is available from the links below. A truly, new highlight of the analysis is the simultaneous two-dimensional fit of top quark pair production cross-section and the branching ratio of top quark to charged Higgs.
In this analysis, I performed a measurement of top quark pair production cross section in the final states consisting of a hadronically decaying tau lepton, a lepton (electron or muon), missing transverse energy, and two or more energetic jets. This is a particularly difficult and challenging analysis: it combines all part of modern particle detector from inner tracking detector all the way to the muon chambers; it utilizes all known object reconstruction algorithm (electron, muon, tau, track, jet, b-jet, and missing energy), and it suffers background from both W and Z production. Using 1 inverse femtobarn of data, we managed to measure a cross-section with about 2.5 sigma significance using additional acceptance from lepton+jets and non-tau dilepton final states. In terms of tau purity, the analysis has a significance of about 1.5-2.0 sigma.
This analysis was approved as preliminary in Summer 2007, and now I am working to update and finalize the analysis for publication as part of cross-section combination with the other dilepton channels. I am also working together to combine this channel with other top pair decay channels in a global search for charged Higgs bosons in top pair decays.
Phenomenology in hadronic physics: Gerasimov-Drell-Hearn sum rule and Regge phenomenology in kaon photoproduction.
My previous work in Indonesia concentrated on the phenomenology of hadronic physics. Specifically I was working on the problem of photoproduction of kaons from nucleon. My previous advisor, Terry Mart, is one of the few experts in this problem. I did two projects with him, one for my B.Sc. thesis, and one for my M.Sc. thesis.
For my B. Sc. thesis, I use a model of Terry's to compute a sum rule which relates the polarized and unpolarized inelastic nucleon's photo-absorption cross section, with the anomalous magnetic moment of the nucleon. The sum rule is known as Gerasimov-Drell-Hearn sum rule (Americans say Drell-Hearn-Gerasimov, whatever). A paper by S.D. Drell (yes, THAT Drell of the Bjorken-Drell books) and A.C. Hearn detailing this sum rule was published in Physical Review Letters 16, 908 (1966).
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For my M. Sc. thesis, I developed a model of kaon photoproduction which is supposed to work from threshold region to the high energy region of 3-4 GeV c.m. energy (well, high with respect to hadronic physics, 5 GeV is NOTHING in the realm of Tevatron). My model was inspired by Terry's model which works from threshold up to 2 GeV c.m. energy, and another model by M. Guidal, J.-M. Laget, and M. Vanderhaeghen which works from around 2.5 GeV up to 4.5 GeV c.m. energy. Combining the works of both, I was able to fit the model to about 750 data points of kaon photoproduction and obtain quite okay, although not excellent, result. As I was leaving Indonesia right after my M. Sc. thesis defense to continue my Ph.D. study at Florida State, I didn't have a chance to follow up this work and publish it.
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The tradition in experimental high energy physics is that a person has the right to be listed in the author list after making significant contribution toward the experiment, not always in the form of physics data analysis. A single publication in experimental high energy physics is always the result of a team of physicists. Depends on the complexity of the physics data analysis, the number of physicists in the team varies greatly. A simple topic may only be the result of two or three people, but a complex topic such as W boson and top masses may be the result of twenty or thirty people working together. Every member of the collaboration always have the right to comment on the publication. In practice, experimental high energy physicists usually separate publications in which they made significant contribution in the data analysis, and other publications in which they only listed as member of the collaboration.
People I am currently working with
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People I had worked with in the past
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Haryo Sumowidagdo
Last modified: Mon Dec 8 18:38:38 CST 2008