Professor K.K. Gan Research

Research:

Physics beyond the Standard Model in e⁺e^- and hadron colliders.

HRS experiment (1982-1985):
A general purpose detector for the study of e⁺e^- collisions using the PEP collider at SLAC.
Thesis advisor: Professor David Koltick
- Study of τ decay. First observation of τ^- → π^-π⁺π^-π⁺π^-ν_τ.
- Maintenance of HRS trigger system.
- Principal author for 2 PRL + 1 PLB (Pub Nos. 1-3).
MARK II experiment (1986-1990):
A general purpose detector for the study of e⁺e^- collisions using the PEP and SLC colliders at SLAC.
Group leader: Nobel Laureate Martin Perl
- Study of τ decay
  - New upper limit on second class current, τ^- → π^-ηντ, contradicting the observation of another experiment.
  - First test of CVC as a function of Q² in τ decay by analyzing the ρ mass spectrum.
- Search for physics beyond the Standard Model
  - Analyzed the implications of a particle (Z') which violates lepton number conservation on the processes e⁺ e^- → μ⁺μ^- and τ⁺τ^-.
  - Study of the sensitivity at high energy e⁺e^- colliders to an exotic lepton and gauge boson.
- Built the vertex detector trigger system. Improved the trigger vertexing resolution by expanding the 10 jet cells into 80 cells through fast digitilization of the signal.
- Principal author for 1 PRL + 2 PRD + 2 PLB (Pub Nos. 4-5, 7-9).
CLEO experiment (1990-2004):
A general purpose detector for the study of e⁺e^- collisions using the Cornell Electron Storage Ring (CESR) at Cornell University.
- Study of τ decay
  - First observation of τ^- → π^-π⁺π^-2π⁰ν_τ and τ^- → π^-ωπ⁰ν_τ; the measured branching ratio for τ^- → π^-π⁺π^-2π⁰ν_τ is significantly larger than that for its isospin partner τ^- → π^-π⁺π^-π⁺π^-ν_τ (PRL).
  - First evidence for τ^- → K^-2π⁰ν_τ (PRL).
  - Most precise measurement of five-charged-pion final states; the measured branching ratio is significantly smaller than those of two other experiments (PRL).
  - First observation of τ^- → K^-ην_τ (PRL).
  - New stringent limits on the forbidden decays of τ into e or μ plus one or two π⁰ or η (PRL).
  - New stringent limit on the decay τ^- → 4π^-3π⁺(π⁰)ν_τ (PRD).
  - Precise measurement of τ^- → π^-π⁺π^-3π⁰ν_τ (PRL); the measured branching ratio is an order of magnitude smaller than that measured by another experiment. First observation of τ^- → π^-ω2π⁰ν_τ.
  - First observation of the decay τ^- → K^*-ην_τ (PRL).
  - New limits on baryon and lepton number violating decays of the τ Lepton (PRD).
  - New measurements of τ^- decays to six pions and a neutrino, including the first observation of the decay τ^- → 2π^-π⁺ων_τ (PRL).
  - New limits on Neutrinoless τ decays involving K⁰ meson (PRD).
  - Study of τ decays to four-hadron final states with kaons, including the first observation of the decay τ^- → K^-ων_τ (PRL).
- Search for the exotic decay η → e⁺e^- as a test of the Standard Model (PRD).
- Derive the procedure for incorporating the statistical uncertainty in the background estimate into the upper limit on the signal (NIM).
- Project leader for the study of helium-based drift chamber gases for CLEO III. The study shows that the spatial resolution of helium-based gases is much better than the argon-based gas used by CLEO II, while the dE/dx resolution is comparable (NIM). The study played a major role in the CLEO II decision to switch to helium-based gas in Fall 1995.
- Project leader of the research and development of the hybrid for the new silicon detector at CLEO III. The hybrid is a card with 24 chips for high voltage biasing, signal amplification, digitization, and sparsification. The card has 3000 wire bonds in a volume of 3 cm x 6 cm x 4 mm. The hybrids were prototyped using a novel combination of FR-4 and BeO. This resulted in major cost saving and allowed the rapid prototyping of various ideas.
- Principal author for 9 PRL + 4 PRD + 2 NIM (Pub Nos. 10-25).
Papers in Proceedings (Since 1995):
Conference Talks:
ATLAS experiment (1998-present):
OSU Faculty: K.K. Gan, Harris Kagan, and Richard Kass
ATLAS is a general purpose detector for the study of pp collisions at 14 TeV center-of-mass energy using the LHC collider at CERN. The collider is the highest energy and luminosity collider in the world. One of the major physics goal of the collider is to discover the Higgs, the particle responsible for generating mass of all particles. We are part of the pixel detector group. The pixel detector is the tracking device closest to the interaction region and is designed to improve the charged particle tracking and identification of b quarks in hadronic jets, critical for the Higgs search.
The extreme high energy of the LHC allows us to look for physics beyond the Standard Model. Lepton signatures have been used in the past for several major discoveries. The OSU groups therefore concentrate on using leptons as a tool in the searches for new physics, including the use of W and Z reconstructed in the leptonic decay modes. We can't list the ongoing searches publicly. However, we can provide links to two published analyses that we participated, study of WZ and ZZ productions.
The ATLAS pixel detector consists of three barrel layers and three forward and backward disks. The primary contribution of the OSU group is in the R&D, design, fabrication, and maintenance of the on-detector radiation-hard and high-speed optical communication. We built the fiber optic transceiver boards (opto-board) for the optical links. Each board contains both optical and electrical components, VCSELs, PINs, DORICs, and VDCs. The differential hit signal (LVDS) from the pixel electronics is converted by the VCSEL Driver Chip (VDC) on a board into a single-ended signal appropriate to drive a Vertical Cavity Surface Emitting Laser (VCSEL) and transmitted to the readout system using a fibre. The 40-MHz beam-crossing clock, encoded with the command signal to control the pixel electronics, is transmitted to a PIN diode via a fibre. The signal from the PIN diode is decoded using a Digital Opto-Receiver Integrated Circuit, DORIC. We use VCSEL and PIN diodes that are fabricated in the highly compact array and each array couples to a fibre ribbon inside an optical package (opto-pack). An opto-board contains one 8-channel PIN array opto-pack and one or two 8-channel VCSEL array opto-packs couple to two 4-channel DORICs and two or four 4-channel VDCs. OSU responsibilities include the design and testing of the radiation-hard VDC and DORIC, and the design, fabrication, and testing of opto-boards. The research is performed in collaboration with Siegen and Academic Sinica (Taiwan). The opto-board assembly document is available at here.
ATLAS plans to add a new pixel layer to the pixel detector in 2013. We propose to continue the use of the VCSEL and PIN arrays for this new generation of opto-links. In addition, we are developing an updated version of the chips in the 130 nm CMOS process with redundancy to bypass a broken PIN or VCSEL channel. For the so-called high luminosity LHC (HL-LHC) upgrade in 2020, we propose the continue use of the optical arrays for three reasons, compact, efficient, and robust, which we much appreciate after 10 years of experience in using the devices. The upgrade will take advantage of the work done by the GBT and VL projects at CERN. In collaboration with Siegen and NIKHEF, we are conducting R&D to enable such deployment.
OSU has perhaps the best equipped optical electronics lab for high energy physics research in US. The lab includes two automatic wire bonders (K&S 1470 and 8060), two manual wire bonders, wire-bond pull tester, dice probe station, high speed scope (6 GHz/20 GS/s), optical spectrum analyzer (OSA), optical comparator, precision vision measuring machine, fiber polisher and fusion splicer, high power UV light, precision scale (0.1 mg), high resolution IR camera, one humidity chamber, and two environmental chambers and ovens. The equipment are funded in part by a Major Research Instrumentation (MRI) grant of NSF. They are housed in the clean room and the adjacent staging room of the new physics building.
More technical information is available at Amir Rahimi, Jason Moore, and Shane Smith web sites.
Talks:
Papers:
- An MT-Style Optical Package for Optical Data Transmission (NIM)
- ATLAS Pixel Opto-Electronics (NIM)
- An MT-Style Optical Package for VCSEL and PIN Arrays (NIM)
Papers in proceedings:
Linear Collider R&D:

Talks:
Research in Teaching:

Papers:

Research:

HRS experiment (1982-1985):

MARK II experiment (1986-1990):

CLEO experiment (1990-2004):

ATLAS experiment (1998-present):

Linear Collider R&D:

Research in Teaching: