B-physics at CDF (open access)

B-physics at CDF

During the 1988/1989 run at the Fermilab Tevatron, the CDF detector collected {approx equal}4.1 pb{sup {minus}1} of p{bar p} data at {radical}s = 1.8 TeV. The main goals of this run being physics at high p{sub t}, the CDF trigger was tuned'' for maximizing signals from Z{sup 0}s, Ws, t-quarks, etc. As such, compared to the high p{sub t} physics, the b-physics program was of secondary importance other than that which would be used for background calculations. Also, CDF had no vertex chamber capability for seeing displaced vertices. However, significant b-quark, physics results are evident in two data samples; inclusive electrons and inclusive J/{psi} where J/{psi} {yields} {mu}{sup +}{mu}{sup {minus}}. We can then ask ourselves, given all this, why is it that CDF is able to do b-quark physics The answer is that nature has been kind enough to provide b-quarks at an extremely high rate at the Tevatron. The production cross-section for b{bar b} production is quite large. In the rest of this paper, I will try to specify the goals for b-physics using the inclusive electrons and J/{psi} signals for the 1988/1989 data set. I will then provide a brief look at the data, and will finish with …
Date: December 10, 1990
Creator: Baden, A.R. (Harvard Univ., Cambridge, MA (USA))
System: The UNT Digital Library
Dielectronic recombination into Rydberg levels of lithiumlike titanium (open access)

Dielectronic recombination into Rydberg levels of lithiumlike titanium

To characterize line formation near threshold for electron-impact excitation, dielectronic capture into high-n levels in lithiumlike Ti{sup 19+} ions has been studied with high-resolution x-ray spectroscopy on the Livermore electron beam ion trap. The process is shown to result in satellite lines which are virtually indistinguishable from their dipole-allowed heliumlike parent lines. High-n satellite lines are absent from dipole-forbidden heliumlike lines.
Date: October 10, 1990
Creator: Beiersdorfer, P.; Chantrenne, S.; Chen, M. H.; Marrs, R. E.; Vogel, D. A.; Wong, K. L. et al.
System: The UNT Digital Library
QCD studies at the hadron colliders (open access)

QCD studies at the hadron colliders

Two hadron collider experiments are actively pursuing QCD jet analyses. They are CDF, with a {radical}s = 1800 GeV, and UA2, with a {radical}s = 630 GeV. Recent results from these collaborations are discussed. The inclusive jet spectrum, dijet mass and angular distribution are compared to QCD predictions and used to set limits on quark substructure. Data from both experiments are compared to the O({alpha}{sub s}{sup 3}) calculations for the inclusive jet cross section. Studies of 3-jet, 4-jet and 5-jet events are described. A limit is set on the cross section for double parton scattering from the UA2 4-jet analysis. The inclusive photon cross section has been measured by both CDF and UA2 and is compared to theoretical predictions. 13 refs., 17 figs., 1 tab.
Date: August 10, 1990
Creator: Flaugher, B.L.
System: The UNT Digital Library
Recent results from hadron colliders (open access)

Recent results from hadron colliders

This is a summary of some of the many recent results from the CERN and Fermilab colliders, presented for an audience of nuclear, medium-energy, and elementary particle physicists. The topics are jets and QCD at very high energies, precision measurements of electroweak parameters, the remarkably heavy top quark, and new results on the detection of the large flux of B mesons produced at these machines. A summary and some comments on the bright prospects for the future of hadron colliders conclude the talk. 39 refs., 44 figs., 3 tabs.
Date: December 10, 1990
Creator: Frisch, H.J. (Chicago Univ., IL (USA))
System: The UNT Digital Library
Characterization of the plasma-switch interaction in the LBL HIF ion source (open access)

Characterization of the plasma-switch interaction in the LBL HIF ion source

A new way to characterize the performance of the LBL HIF ion source has been found. In the LBL source, ions are drawn from an arc-generated plasma reservoir in which the electrons are confined by a negative-biased switch'' mesh. Stagnation of the plasma is prevented by absorption of the excess ion flow on this mesh. The ion beam is generated by an external negative voltage that provides Child-Langmuir extraction of the ions through the switch mesh. We elucidate the physics requirements of the source and deduce switch mesh parameters needed for successful operation. 2 refs., 2 figs.
Date: December 10, 1990
Creator: Hewett, D.W. (Lawrence Livermore National Lab., CA (USA)) & Rutkowski, H.L. (Lawrence Berkeley Lab., CA (USA))
System: The UNT Digital Library
Start-effect measurement of high FEL (free-electron laser) electric fields in MTX (Microwave Tokamak Experiment) by laser-aided particle-probe spectroscopy (open access)

Start-effect measurement of high FEL (free-electron laser) electric fields in MTX (Microwave Tokamak Experiment) by laser-aided particle-probe spectroscopy

We are constructing a diagnostic system to measure the electric field (>100 kV/cm) of a free-electron laser (FEL) beam when injected into the plasma of the Microwave Tokamak Experiment (MTX). The apparatus allows a crossed-beam measurement, with 2-cm spatial resolution in the plasma, involving the FEL beam (with 140-GHz, {approx}1-GW ECH pulses), a neutral-helium beam, and a dye-laser beam. After the laser beam pumps metastable helium atoms to higher excited states, their decay light is detected by an efficient optical system. Because of the Stark effect arising from the FEL electric field ({rvec E}), a forbidden transition can be strongly induced. The intensity of emitted light resulting from the forbidden transition is proportional to E{sup 2}. Because photon counting rates are estimated to be low, extra effort is made to minimize background and noise levels. It is possible that the lower {rvec E} of an MTX gyrotron-produced ECH beam with its longer-duration pulses can also be measured using this method. Other applications of the apparatus described here may include measurements of ion temperature (using charge-exchange recombination), edge-density fluctuations, and core impurity concentrations.
Date: May 10, 1990
Creator: Oda, T.; Takiyama, K. (Hiroshima Univ. (Japan)); Odajima, K.; Ohasa, K.; Shiho, M. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan)); Mizuno, K. (California Univ., Davis, CA (USA) Lawrence Livermore National Lab., CA (USA)) et al.
System: The UNT Digital Library
Hadron supercolliders: The 1-TeV scale and beyond (open access)

Hadron supercolliders: The 1-TeV scale and beyond

Greater understanding of the connection between the weak and electromagnetic interactions is central to progress in elementary-particle physics. A definitive exploration of the mechanism for electroweak symmetry breaking will require collisions between fundamental constituents at energies on the order of 1 TeV. This goal drives the design of high-energy, high-luminosity hadron colliders that will be commissioned during the next decade, but by no means completely defines their scientific potential. These three lectures are devoted to a review of the standard-model issues that motivated an experimental assault on the 1-TeV scale, an introduction to the machines and the experimental environment they will present, and a survey of possibilities for measurement and discovery with a multi-TeV hadron collider. 72 refs., 29 figs.
Date: August 10, 1990
Creator: Quigg, C.
System: The UNT Digital Library
The e sup + , e sup minus background at Relativistic Heavy Ion Collider (RHIC) generated by beam crossing (open access)

The e sup + , e sup minus background at Relativistic Heavy Ion Collider (RHIC) generated by beam crossing

At the Brookhaven Relativistic Heavy Ion Collider (RHIC), fully stripped heavy ions will circulate in each of two rings up to beam energies of 250 (Z/A) GeV/u. During the beam crossing, the peripheral electromagnetic interaction between the heavy ions is sufficient to induce copious production of di-lepton pairs. These pairs are a potential source of background for the detectors at RHIC. In this paper we discuss the expected number of e{sup +},e{sup {minus}} pairs, given the accepted initial luminosity value L of the collider. More importantly, we also calculate the differential cross sections for the angle, energy, rapidity and momentum distribution of the leptons. Using the luminosity L of the collider, these differential cross sections are normalized to the expected number of leptons per second. We restrict ourselves to e{sup +},e{sup {minus}} production, a discussion of {mu}{sup +},{mu}{sup {minus}} and {tau}{sup +}{tau}{sup {minus}} distributions will be published later. The results are presented for the expected worst case, namely {sup 197}Au{sup 79+} ions at a beam kinetic energy of 100 GeV/u. This is forseen to be the heaviest ion for high luminosity experiments at RHIC. We note for a given energy, the cross section for e{sup +},e{sup {minus}} production scales as …
Date: August 10, 1990
Creator: Rhoades-Brown, M.J.; Ludlam, T. (Brookhaven National Lab., Upton, NY (USA)); Wu, J.; Bottcher, C. & Strayer, M. (Oak Ridge National Lab., TN (USA))
System: The UNT Digital Library
Collective Effects in Short Bunches: Summary of the Working Group on Proton Bunches (open access)

Collective Effects in Short Bunches: Summary of the Working Group on Proton Bunches

This report discusses the following topics on proton beam bunching: space charge, a collective but incoherent effect; a very short proton bunch; long proton bunches; transition energy crossing; intrabeam scattering; vacuum related effects; and the issue of mode-coupling for proton bunches. (LSP)
Date: October 10, 1990
Creator: Ruggiero, Alessandro G.
System: The UNT Digital Library
Use of a FEL (free electron laser) as a buncher for a TBA (two-beam accelerator) scheme (open access)

Use of a FEL (free electron laser) as a buncher for a TBA (two-beam accelerator) scheme

S. S. Yu has proposed an alternate injector for the drive beam. A linear induction accelerator (LIA) produces a beam of several kA, having an energy more than 10 MeV, and with a pulse length about 12 ns long. This beam energizes a 29 GHz rf FEL amplifier. The exiting beam is well modulated at 29 GHz and is then chopped in a subharmonic transverse chopper at 352 MHz. The resulting pulse has the requisite temporal format for the drive beam and is subsequently accelerated by means of the LEP 352 MHz cavities to several GeV. One additional requirement is demanded of the low energy drive beam: it must have small energy spread, less than about 10%, lest the beam become debunched or lost through chromatic aberrations in the low energy magnetic optics prior to acceleration to several GeV. This paper examines Yu's concept. In Section 2, the FEL performance is explored. Questions of the design of the subharmonic buncher and debunching of the beam subsequent to exiting from the FEL are considered in Section 3. Sections 4 contains the conclusions and suggestions for future directions.
Date: September 10, 1990
Creator: Shay, H. D.; Jong, R. A.; Ryne, R. D.; Scharlemann, E. T. & Yu, S. S.
System: The UNT Digital Library
Recent QCD results from CDF (open access)

Recent QCD results from CDF

In this paper we report recent QCD analysis with the new data taken from CDF detector. CDF recorded an integrated luminosity of 4.4 nb{sup {minus}1} during the 1988--1989 run at center of mass system (CMS) energy of 1.8 TeV. The major topics of this report are inclusive jet, dijet, trijet and direct photon analysis. These measurements are compared of QCD predictions. For the inclusive jet an dijet analysis, tests of quark compositeness are emphasized. 11 refs., 6 figs.
Date: October 10, 1990
Creator: Yun, J.C.
System: The UNT Digital Library