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Physics with low-energy e/sup +/e/sup /minus// and e/sup /minus//e/sup /minus// collisions at Tau-Charm Factory

Description: The physics opportunities in e/sup /plus//e/sup /minus// collisions with /radical/s /approx equal/ 1-2 GeV and e/sup /minus//e/sup /minus// collisions with /radical/s /approximately/5 GeV at Tau-Charm Factory are being explored. The low-energy e/sup /plus//e/sup /minus// option allows precise measurements of e/sup /plus//e/sup /minus// cross sections into /pi/'s and /eta/'s and hence stringent tests of the conserved-vector-current (CVC) hypothesis in /tau/ decays. Precise measurement of the total hadronic cross section also permits a more precise calculation of the muon anomalous magnetic moment (g-2). The e/sup /minus//e/sup /minus// option provides an opportunity for a sensitive search for lepton-number violating processes e/sup /minus//e/sup /minus// /yields/ /mu//sup /minus///mu//sup /minus//, /tau//sup /minus///tau//sup /minus//, /mu//sup /minus///tau//sup /minus// .... The e/sup /minus//e/sup /minus// collider also provides an ideal laboratory for two-photon physics with no one-photon background and the direct measurement of the two-photon background in one-photon physics 19 refs., 4 figs.
Date: July 1, 1989
Creator: Gan, K.K.
Partner: UNT Libraries Government Documents Department

Multiple-neutral-meson decays of the /tau/ lepton and electromagnetic calorimeter requirements at Tau-Charm Factory

Description: This is a study of the physics sensitivity to the multiple-neutral-meson decays of the /tau/ lepton at the Tau-Charm Factory. The sensitivity is compared for a moderate and an ultimate electromagnetic calorimeter. With the high luminosity of the Tau- Charm Factory, a very large sample of the decays /tau//sup /minus// /yields/ /pi//sup /minus//2/pi//sup 0//nu//sub /tau// and /tau//sup /minus// /yields/ /pi//sup /minus//3/pi//sup 0//nu//sub /tau// can be collected with both detectors. However, with the ultimate detector, 2/pi//sup 0/ and 3/pi//sup 0/ can be unambiguously reconstructed with very little background. For the suppressed decay /tau//sup /minus// /yields/ /pi//sup /minus///eta//pi//sup 0//nu//sub /tau//, only the ultimate detector has the sensitivity. The ultimate detector is also sensitive to the more suppressed decay /tau//sup /minus// /yields/ K/sup /minus///eta//nu//sub /tau// and the moderate detector may have the sensitivity if the hadronic background is not significantly larger than that predicted by Lund. In the case of the highly suppressed second-class-current decay /tau//sup /minus// /yields/ /pi//sup /minus///eta//nu//sub /tau//, only the ultimate detector has sensitivity. The sensitivity can be greatly enhanced with a small-angle photon veto. 16 refs., 9 figs., 2 tabs.
Date: August 1, 1989
Creator: Gan, K.K.
Partner: UNT Libraries Government Documents Department

New results on the tau lepton

Description: This is a review of new results on the tau lepton. The results include precise measurements of the lifetime, measurements of the decay tau/sup -/ ..-->.. ..pi../sup -/2..pi../sup 0/nu/sub tau/ with much improved precision, and limits on decay modes containing eta mesons, including the second-class-current decay tau/sup -/ ..-->.. ..pi../sup -/eta nu/sub tau/. The implications of these new results on the discrepancy in the one-charged-particle decay modes are discussed. 52 refs., 6 figs., 2 tabs.
Date: November 1, 1987
Creator: Gan, K.K.
Partner: UNT Libraries Government Documents Department

Limits on a lepton number violating process in e/sup +/e/sup -/ collisions

Description: If a new hypothetical particle induces a lepton number violating process, it could also affect e/sup +/e/sup -/ ..-->.. ..mu../sup +/..mu../sup -/ and /tau//sup +//tau//sup -/ through its t-channel exchange. A fit of the measured cross sections and forward-backward asymmetries at PEP and PETRA yields the 90% CL limits on the coupling of the particle: G/sub e..mu../ < 0.119G/sub F/ and G/sub er/ < 0.085G/sub F/, where G/sub F/ is the Fermi coupling constant. These limits exclude certain regions of couplings allowed by other lepton number violation searches. 6 refs., 2 figs., 1 tab.
Date: October 1, 1988
Creator: Gan, K.K.
Partner: UNT Libraries Government Documents Department

Searching for an exotic lepton and gauge boson at high energy e/sup +/e/sup /minus// colliders

Description: The possibility of searching in high energy e/sup +/e/sup /minus// collisions for a singly produced heavy with an ordinary light lepton, e/sup +/e/sup /minus// ..-->.. L/sup +//ell//sup /minus//, has been investigated. The search is motivated mainly by its distinctive experimental signatures. In a data sample corresponding to an integrated luminosity of 30 fb/sup /minus/1/ collected at a 1 TeV e/sup +/e/sup /minus// collider, the search is sensitive to a lepton of mass up to about 1 TeV/c/sup 2/ and a production cross section as low as 10% of the ..mu..-pair point cross section. For the case where the process is mediated by an exotic gauge boson, sensitivity to a gauge boson of mass up to about 2 TeV/c/sup 2/ can be achieved. 5 refs., 7 figs., 2 tabs.
Date: January 1, 1989
Creator: Gan, K.K.
Partner: UNT Libraries Government Documents Department

Review of recent results on the /tau/ lepton

Description: This is a review of the recent results on the /tau/ lepton. The results include precise measurements of the lifetime, measurements of the decay /tau//sup /minus// ..-->.. ..pi../sup /minus//2..pi../sup 0/..nu../sub /tau// with much improved precision, limits on decay modes containing /eta/ mesons, including the second-class-current decay /tau//sup /minus// ..-->.. ..pi../sup /minus///eta/..nu../sub /tau//, and limits on exotic decay modes. The implications of these results on the discrepancy in the one-charged-particle decay modes are discussed. 43 refs., 4 figs., 2 tabs.
Date: April 1, 1988
Creator: Gan, K.K.
Partner: UNT Libraries Government Documents Department

Development of Single Crystal Chemical Vapor Deposition Diamonds for Detector Applications

Description: Diamond was studied as a possible radiation hard technology for use in future high radiation environments. With the commissioning of the LHC expected in 2009, and the LHC upgrades expected in 2013, all LHC experiments are planning for detector upgrades which require radiation hard technologies. Chemical Vapor Deposition (CVD) diamond has now been used extensively in beam conditions monitors as the innermost detectors in the highest radiation areas of BaBar, Belle and CDF and is installed in all LHC experiments. As a result, this material is now being discussed as an alternative sensor material for tracking very close to the interaction region of the super-LHC where the most extreme radiation conditions will exist. Our work addressed the further development of the new material, single-crystal Chemical Vapor Deposition diamond, towards reliable industrial production of large pieces and new geometries needed for detector applications.
Date: March 31, 2009
Creator: Kagan, Harris; Gan, K.K. & Kass, Richard
Partner: UNT Libraries Government Documents Department

Design and Fabrication of a Radiation-Hard 500-MHz Digitizer Using Deep Submicron Technology

Description: The proposed International Linear Collider (ILC) will use tens of thousands of beam position monitors (BPMs) for precise beam alignment. The signal from each BPM is digitized and processed for feedback control. We proposed the development of an 11-bit (effective) digitizer with 500 MHz bandwidth and 2 G samples/s. The digitizer was somewhat beyond the state-of-the-art. Moreover we planned to design the digitizer chip using the deep-submicron technology with custom transistors that had proven to be very radiation hard (up to at least 60 Mrad). The design mitigated the need for costly shielding and long cables while providing ready access to the electronics for testing and maintenance. In FY06 as we prepared to submit a chip with test circuits and a partial ADC circuit we found that IBM had changed the availability of our chosen IC fabrication process (IBM 6HP SiGe BiCMOS), making it unaffordable for us, at roughly 3 times the previous price. This prompted us to change our design to the IBM 5HPE process with 0.35 ┬Ám feature size. We requested funding for FY07 to continue the design work and submit the first prototype chip. Unfortunately, the funding was not continued and we will summarize below the work accomplished so far.
Date: September 12, 2008
Creator: Gan, K.K.; Johnson, M.O.; Kass, R.D. & Moore, J.
Partner: UNT Libraries Government Documents Department

Alignment of the Pixel and SCT Modules for the 2004 ATLAS Combined Test Beam

Description: A small set of final prototypes of the ATLAS Inner Detector silicon tracking system(Pixel Detector and SemiConductor Tracker), were used to take data during the 2004 Combined Test Beam. Data were collected from runs with beams of different flavour (electrons, pions, muons and photons) with a momentum range of 2 to 180 GeV/c. Four independent methods were used to align the silicon modules. The corrections obtained were validated using the known momenta of the beam particles and were shown to yield consistent results among the different alignment approaches. From the residual distributions, it is concluded that the precision attained in the alignmentof the silicon modules is of the order of 5 mm in their most precise coordinate.
Date: June 2, 2008
Creator: Collaboration, ATLAS; Ahmad, A.; Andreazza, A.; Atkinson, T.; Baines, J.; Barr, A.J. et al.
Partner: UNT Libraries Government Documents Department