Willis K. Sakumoto Senior Scientist
(and Senior Laboratory Engineer)
Experimental High Energy Physics
Fermilab MS 318
(630) 840-8431; Rochester Secretary (585) 275-5306
Fermilab: (630) 840-2968; Rochester: (585) 273-3237
Biographical SketchWillis K. Sakumuto received his B.S. in Physics (1972) from the Illinois Institute of Technology, and his Ph.D. in Physics (1983) from the Northwestern University. He was a postdoctoral associate at Rochester from 1984-1990, promoted to Senior Research Associate in 1990, and appointed Senior Laboratory Engineer and Senior Scientist in 2003. Sakumoto co-managed the production and installation of the CDF Run II end plug hadron calorimeter upgrade with senior scientists Howard Budd and Pawel de Barbaro (1992-1996). He has also served as co-convenor of CDF's Top/Electroweak Physics Group (2001-2003).
Research ActivitiesSakumoto's research interest is in the field of Experimental High Energy Physics. His Ph.D. thesis research, supervised by Prof. Jerome L. Rosen at Northwestern, was a search for charmed particles produced in pion-Be interactions using a prompt muon trigger (Fermilab experiment E515).
Sakumoto's research interests are in the physics of W's, Z's and dileptons (CDF), in neutrino physics (CCFR/NuTeV), and in electron-nucleon scattering experiments. In the area of instrumentation, Sakumoto's research is on scintillating tile with optical-fiber hadron calorimeters. Sakumoto is currently involved mostly on the CDF experiment.
Sakumoto's previous research included his thesis research, a search for charmed particles produced in hadron collision using a prompt muon trigger (E515). His primary responsibility involved the sampling lead/liquid-argon electromagnetic calorimeter: its construction, installation, operation (cryogenics and readout electronics), and data analysis.
In 1984, he joined the CCFR collaboration to study neutrino interactions with the Fermilab Lab E detector using Tevatron Quadrupole-Triplet wide band neutrino beam. The beam is the highest energy neutrino beam, with energies up to 600 GeV. He participated in the 1985 (E744) and 1987 (E770) neutrino data runs. Before the 1987 run, he upgraded the data acquistion (DAQ) system and readout hardware to improve its reliablity and performance. During the runs, he maintained the trigger and calorimetry counters, and their associated electronics. Sakumoto's major contribution was the measurement, understanding, and maintainance of the target calorimeter's energy response, and calibration to a level of 1% over a large transverse area. This was crucial for precision structure function measurements in a wide band neutrino beam. Saumoto designed and implemented the calibration of the calorimeter in a hadron test beam including all of the analysis and calibration software.
Sakumoto also worked on neutrino induced production of both same-sign and opposite-sign dimuon pairs. During the mid-1980's measurements of the same-sign dimuon rate exceeded standard model predictions. The new physics suggested by these measurements was disproved by CCFR. A key part of the CCFR measurement is a better understanding of the muon background from hadron showers. This also helped the measurement of the nucleon's strange sea using opposite-sign dimuons, which are associated with c-quark production from d and s quarks. Sakumoto worked on the analysis of hadron punchthrough and muon-production from hadron showers in the Lab E calorimeter using hadron test beam data, and published a measurement of the particle punchthrough rate across absorbers of various lengths. CCFR also took high energy cosmic ray data. Since it contains a substantial amount of TeV energy muons, he measured and published the mean dE/dx and differential energy loss spectra of muons versus its energy. This is important for the design of post-Tevatron, TeV-muon detectors.
After the 1987 run, Sakumoto joined the SLAC electron scattering experiment NE11 to measure the electric and magnetic form factors of the neutron and proton to significantly larger Q2 of 4 and 8.83 GeV2, repectively. The 1.5 and 8 GeV spectrometers at End Station A were used, and he worked on the spectrometer hardware, trigger electronics, and DAQ.
In 1990, he joined the CDF collaboration to upgrade its forward end plug gas calorimeters with a new sampling, scintillator plate calorimeter using the new technology of plastic wavelength shifting optical fiber readouts. This technology was chosen by CDF after successful beam tests of prototypes, including a large engineering prototype, in the 1990-91 test beam runs. Sakumoto was responsible for these beam tests. During the design of the upgrade calorimeters, Sakumoto's physics studies defined the transverse tower segmentation. The Rochester group was given the responsibility for the upgrade of the Run-II end plug hadron calorimeter, including the the design, R&D in support of design and production, procurement of materials, implementation of quality assurance and control (QA/QC) procedures to insure a working detector, and production management at Fermilab. The production ended in 1996. A 60 degree-section replica of the calorimeter was constructed and beam tested over 1996-97. Sakumoto supervised the assembly and checkout of various portions of the test beam module and implemented the online event display and the event reconstruction system. Subsequently Sakumoto participated in the design, implementation, and analysis of a series of beam tests that measured the performance of the calorimeters. During the 1997-98 installation of the Run II end plug calorimeters at the collision hall, Sakumoto provided technical supervision for the installation of the hadron scintillation counters and optical cables onto the steel absorber. A novel feature is the use of multi-tile scintillator counter assemblies (Megatiles) with mass terminated optical connectors. The optical signals were transported to readout photomultipliers via multi-fiber optical cables with mass terminated connectors. Sakumoto developed and implemened QA/QC procedures to insure the integrity of the optical and electrical systems. All optical and electrical connections were tested using a radioactive source calibration system. During the 1998-2000 Run II Commissioning, Sakumoto worked on the new calorimetry front end electronics based on the QIE chip, along with the new data aquisition (DAQ) system, and worked on commissioning the plug hadron TDC timing system that provides shower pulse arrival times.
Sakumoto's physics analyses during 1996-2000 focused on Drell-Yan lepton pair production in the Z-boson resonance region using 110 pb-1 of collider data from Run-I. He studied QED radiative corrections to the process and published a PRD article on this in collaboration with theorists. He has also measured and published the transverse momentum and total cross sections of e+e- pairs in the Z-boson resonance region between 66 and 116 GeV/c2. This analysis was extended to include forward e+e- pairs, leading to the publication of the first measurements of the rapidity (y) and the total Z cross sections with full detector rapidity coverage. Sakumoto led the publication efforts of other related physics analyses including Drell-Yan cross section measurements using dimuon pairs and limits of quark-lepton compositeness scales using high mass e+e- and dimuon pairs. Sakumoto also contributed to the Rochester effort that published an improved Run-I e+e- channel measurement of the differential mass distribution and the forward-backward decay asymmetry of these pairs.
Sakumoto served as a co-convenor of the CDF Top and Electroweak physics group from January 2001 to December 2002. From 2001 and onwards, Sakumoto has been a co-leader of the CDF Calorimetry Operations and Reconstruction Group. This involves day-to-day management for all of CDF's calorimeters. In addition, he is the sub-project leader for the end plug calorimeters, and is responsible for their maintenance and performance. With other members of the CDF Rochester group, he has been maintaining the readout optics of the plug electromagnetic and hadronic calorimeters, up to, and including the readout phototubes. The Rochester group also calibrates and maintains the absolute energy scale of each plug calorimetertower for online and offline use. Sakumoto is also the on-call expert for the end plug calorimeter high voltage system.
Sakumoto's CDF Run-II physics interests include the dynamics of Drell-Yan production W and Z bosons and their leptonic decays, and in the measurement of the top quark mass. He is an active participant of the CDF Electroweak physics group's W-Z Cross Section working group and the Top physics group's Jet Corrections working group. The W-Z cross section group is working towards a publication of the W and Z boson total cross sections at a center of mass energy of 1.96 TeV, and a precision extraction of the W-boson decay width from these measurements. Sakumoto has been working on the modeling and tuning of W and Z production dynamics in the simulation, on understanding the systematic efects of parton distribution function errors in the simulation, and on doing numerical calculations on the theoretical predictions of the W and Z total cross sections. He has integrated precision plug calorimeter offline energy calibrations derived from periodic radioactive source and laser calibrations into the CDF physics analysis software infrastructure. Such precision calibrations are needed for jet energy corrections in precision top mass measurements. In addition, he is continuing to develop and implement plug electron identification algorithm and tools for CDF.
For a SLAC/SPIRES List of Sakumotos's publications click (here for full list)
- A PRECISE DETERMINATION OF ELECTROWEAK PARAMETERS IN NEUTRINO NUCLEON SCATTERING (CCFR/NuTeV).
NuTeV Collaboration (G.P. Zeller et al.)
Phys.Rev.Lett. 88, 091802 (2002)
( abstract | download )
- Measurement of d sigma / dM forward backward charge asymmetry for high mass Drell-Yan e+ e- pairs from p anti-p collisions at s**(1/2) =1.8-TeV (CDF).
CDF Collaboration (T. Affolder et al.)
Phys.Rev.Lett. 87, 131802 (2001)
( abstract | download )
- STUDIES OF THE RESPONSE OF THE PROTOTYPE CMS HADRON CALORIMETER, INCLUDING MAGNETIC FIELD EFFECTS, TOPION, ELECTRON, AND MUON BEAMS. (CMS)
CMS-HCAL Collaboration (V.V. Abramov et al.).
Nucl.Instrum.Meth. A457, 75 (2001)
( abstract | download)
click ( here for citation summary format )
For further details and CV, go to Sakumoto's home page at: http://www.pas.rochester.edu/~willis/
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