Fermilab Collider Research Articles

Hyperon production from proton-antiproton collisions at sqrt s =1.8 TeV.

The production properties of lambdas ({Lambda}{sup 0},{bar {Lambda}} {sup 0}) and cascades ({Xi}{sup {minus}},{bar {Xi}} {sup {minus}}) in the central region in {ital {bar p}p} collisions at {radical}{ital s} =1.8 TeV at the Fermilab collider are reported. The transverse-momentum spectra of lambdas are measured as a function of multiplicity and the ratios of lambdas to protons ({ital p},{ital {bar p}}) and to all charged particles are studied as a function of transverse momentum and multiplicity. Moreover the average transverse momentum of cascades and the ratio of cascades to lambdas are presented.

Updated prediction of the top quark mass and implications of its possible confirmation

Using the latest LEP and other precision data, we make what could be the last prediction of the mass of the top quark before its detection during the current Fermilab Collider run: m t=124 −28 +26 GeV within the context of the standard model. We also predict that the standard model Higgs boson should weigh 25 −19 +275 GeV. We present the implications for M H and the parameters of the minimal supersymmetric extension of the standard model if indeed m t=130 GeV, and comment on the implications for the status of other proposed extensions of the standard model such as technicolour.

Control and data acquisition electronics for the CDF silicon vertex detector

A control and data acquisition system has been designed for the CDF silicon vertex detector (SVX) at Fermilab. The system controls the operations of the SVX Rev D integrated circuit (S.A. Kleinfeeder et al., 1988) that is used to instrument a 46000 microstrip silicon detector (W.C. Corithers et al., 1990). The system consists of a Fastbus sequencer, a crate controller, and digitizer modules. The authors describe the hardware design for the CDF SVX data acquisition electronics. The method chosen for integrating the SVX detector system into the CDF data acquisition network and synchronization with the Fermilab collider beam crossings are discussed. The sequencer, controller, and digitizer are described. Error detection and diagnostics are considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Discrimination of $$p\bar p \to t\bar t$$ events by a neural network classifier

Neural network and conventional statistical techniques are compared in the problem of discriminating\(p\bar p \to t\bar t\) events, with top quarks decaying into anything, from the associated hadronic background at the energy of the Fermilab collider. The NN we develop for this sake is an improved version of Kohonen's learning vector quantization scheme. Performance of the NN as a\(t\bar t\) event classifier is found to be less satisfactory than that achievable by statistical methods. We conclude that the probable reasons for the are: i) the NN approach presents advantages only when dealing with event distributions in the feature space which substantially differ from Gaussians; ii) NN's require much larger training sets of events than statistical discrimination in order to give comparable results.

A quark-gluon plasma search in p̄-p at [formula omitted

We present a survey of the recent results of E-735 in its search for QGP signals at the Fermilab Collider. The basic data are the inclusive P t distributions of centrally produced π, K, p̄ and Λ 0 as a function of total charged multiplicity in the collision; the variation of 〈P t〉 and particle ratios are derived. Preliminary results on π-π correlations and inclusive photon production are also presented.

High-luminosity search for highly ionizing particles at the Fermilab collider.

Stacks of polycarbonate, CR-39 plastic, and BP-1 glass sheets were used to record tracks of highly ionizing particles produced in collisions of protons and antiprotons at \ensuremath{\surd}s =1800 GeV, with an integrated luminosity of \ensuremath{\sim}${10}^{34}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$. No monopoles or other highly ionizing penetrating particles were found.

Status of top-quark searches at hadron colliders and present mass limits

We discuss the present top quark searches and lower limits on the top mass from the CERN and Fermilab collider experiments, and what may be expected from the latest data-taking periods of 1988/89. Since with the data of 1989, the mass domain probed should extend up to m t ∼ m W, we discuss some aspects of this t-quark mass range, some experimental hints, and the background of W + ≥ 2 jet events.

Search for heavy stable particles in 1.8-TeV pp-bar collisions at the Fermilab collider.

A search was made for heavy stable charged particles produced in 1.8-TeV proton-antiproton collisions. No such particles were found in 26.2 nb{sup {minus}1} of data. Cross-section limits are presented and mass limits of the order of 100 GeV are set for particles containing excited quarks in higher color representations.

Bounds on new Z bosons.

Since new $Z$ bosons (${Z}^{\ensuremath{'}}$) are predicted by many approaches to particle physics beyond the standard model, the absence of a signal in lepton pairs at hadron colliders implies important, but very model-dependent, lower limits on ${Z}^{\ensuremath{'}}$ masses. We present an analytical procedure for converting an experimental limit on $\ensuremath{\sigma}({Z}^{\ensuremath{'}})B({Z}^{\ensuremath{'}}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}})$ into mass limits in a large set of models. Explicit results are given for present CERN and future Fermilab collider data. We include renormalization effects so that consideration can be restricted to grand-unification models.

Probing vacuum stability bounds at the fermilab collider

If the top quark mass is above 86 GeV, then a stringent lower bound on the mass of the Higgs boson arises from the requirement of vacuum stability. We calculate the bound as precisely as possible by numerically solving the renormalization group equations to two-loop order. If the lower bound on the top mass is 100 (110, 120) GeV, the lower bound to the Higgs mass is found to be 20 (34, 50) GeV. Thus, if the standard model is correct, then a nondiscovery of the top quark at the Fermilab Collider implies that the Higgs boson cannot be discovered at CUSB, SLC or LEP I.

Lambda 0 and Lambda -bar0 production from proton-antiproton collisions at sqrt s =1.8 TeV.

The transverse-momentum spectra of lambdas (${\ensuremath{\Lambda}}^{0}, {\overline{\ensuremath{\Lambda}}}^{0}$) produced in the central region has been measured in $\overline{p}p$ collisions at $\sqrt{s}=1.8$ TeV at the Fermilab Collider. We find that the average transverse momentum of the lambdas increases more rapidly with center-of-mass energy than that of charged particles, and the ratio of lambdas to charged particles increases as a function of center-of-mass energy.

Design and performance of a time-of-flight system for particle identification at the Fermilab collider

The design and performance of a TOF system used in a Fermilab collider experiment is evaluated in terms of time, mass, and spatial resolution. The system is designed to survive in a high rate and high background environment. The overall time resolution of the TOF system is measured to be σ = 110 ps.

Test results from a precision drift chamber vertex detector prototype using dimethylether

Results of beam tests of a prototype drift chamber vertex detector developed for the D-Zero experiment at the Fermilab collider are reported. The chamber design emphasizes dual goals of high accuracy position measurement and excellent two track resolution. These requirements are met by using a slow gas, dimethyl ether, in a jet chamber geometry with a double plane of field-shaping wires near the anodes. Resolution of nearby hits is facilitated by 100 MHz flash digitization of the signal pulses. The prototype tested consisted of a full-length (97 cm) model of one azimuthal sector of the innermost layer of the detector, with 8 anode wires. Position measurement accuracy of 30–80 μm for drift distances of 2–11 mm and pulse pair resolution of 0.7 mm (for 90% of all pulses) is achieved.

First Events and Prospects at the Fermilab Collider

A brief description of the Collider Detector at Fermilab (CDF) is given including the detector components and the data acquisition system. The first test run, the first events, and the performance of the detector are discussed. Finally the prospects for future running are reviewed.

Drift-pots for small angle elastic scattering at the fermilab collider

In order to measure the small angle p- p scattering at the Fermilab Tevatron collider we developed very small drift chambers integrated with thin-wall roman pots. We named them drift-pots. The drift-pots are active 100 μm from the vacuum of the beam with an expected resolution of 60 μm in the drift direction and 250 μm in charge division. They are radiation resistant detectors intrinsically insensitive to the beam pickup pulses and their multiple hit readout capability will allow us to push them into the beam halo where p- p Coulomb elastic scattering dominates. For our application, we belive the drift-pots, are superior to state of the art silicon detectors.

Gluino and squark search at Tevatron collider energies

Event rates and distributions for high mass gluinos and squarks are computed at Tevatron collider energies, imposing experimentally realisticP T cuts. Gluino and squark masses can be probed up to 200 GeV at $$\sqrt s = 2 TeV$$ , and up to about 150 GeV at $$\sqrt s = 1.6 TeV$$ with the supersymmetric signal being much more enhanced relative to the standard model background than at CERN $$\bar p$$ energies. If the CERN UA1 missing-p T events are indeed indicative for the existence of gluinos and/or squarks with masses of about 50–70 GeV, then the Fermilab collider experiments should easily confirm the expected huge supersymmetric signals.

Prospects for supersymmetry at the Fermilab collider.

We compute cross sections for production of pairs of strongly interacting supersymmetric (SUSY) particles in pp\ifmmode\bar\else\textasciimacron\fi{} collisions as a function of collider energy. For a scalar-quark or gluino mass of 80 GeV, we find that the ratio of the SUSY cross section to the standard-model background increases by a factor of about 10 when \ensuremath{\surd}s is increased from 630 to 1600 GeV. If decays to photinos are dominant, we show that in the first 2 years of running, experiments at the Fermilab Tevatron collider should be sensitive to gluino (scalar-quark) masses up to at least ${m}_{g\ifmmode \tilde{}\else \~{}\fi{}}$=150 GeV (${m}_{q\ifmmode \tilde{}\else \~{}\fi{}}$=120 GeV). We show characteristic missing-${p}_{T}$ distributions expected if SUSY particles with such masses are produced. For SUSY particles of large mass, we stress the importance of scalar-quark and gluino decays to W and Z gauginos.

A Large Dynamic Range Charge Amplifier ADC for the Fermilab Collider Detector Facillity

A multi-channel charge amplifier ADC system for use with electromagnetic and hadronic calorimetry has been built with Xl and X16 amplifier channels which extend the range of the single 16 bit ADC to the equivalent of a 20 bit system having 0.7 fC least significant resolution. Two on-board calibration schemes, a fast analog trigger output, and redundant readout are also included. The point-wise error in linearity (expressed as the maximum error as a percentage of the full charge scale) is less than 0.02% for the Xl channels, and less than 0.002% for the X16 channels. Other features include a Before/After signal differencing scheme which provides low frequency noise rejection and compensation for baseline drifting, and temperature stability on the order of 30 ppm/C.

Software for Initializing Multi-Segment FASTBUS Systems

Before becoming fully operational, a FASTBUS system must be initialized; each segment interconnect (SI) must be downloaded with the correct route table, group address (GP) assignments must be made to each segment, etc. Furthermore, each system component must be initialized in the correct order; a given segment cannot be accessed until all SIs on the path to that segment have been initialized. It is desirable that the initialization procedure be automatic (i.e., requires no. human intervention), be driven from a database containing the system topology and information of all devices in the system, and assure that the system is placed in a completely specified state regardless of the initial state. This paper presents an algorithm for doing this whicn nas been successfully implemented at the Fermilab Collider Detector Facility (CDF).

Construction and testing of a 3 m diameter × 5 m superconducting solenoid for the fermilab collider detector facility (CDF)

A thin 3 m diameter × 5 m, 1.5 T superconducting solenoid for the Fermilab collider detector facility (CDF solenoid) was constructed. Cool-down and excitation tests of the solenoid were carried out. The design current is 5000 A and the stored magnetic energy is 30 × 10 6 J. The solenoid utilizes the forced flow cooling method of two-phase helium and does not have a permanent inner bobbin. The material thickness of the solenoid is 0.85 radiation length in the radial direction. An aluminum-stabilized NbTi/Cu superconductor fabricated with the EFT method was used. Radially outward magnetic forces must be supported with an outer support cylinder shrink-fitted outside the coil. The helium cooling tube of 20 mm in inner diameter and about 140 m in length was welded to the outer support cylinder. The maximum excitation current was limited to 2800 A in the present tests without an iron return yoke. Thermal response of the solenoid during the cool-down and excitation tests was very steady. A series of heater quench tests was attempted by using a heater installed at the outer support cylinder. The solenoid did not quench even for a heater input of about 10 kJ. In a warm-up test the liquid helium supply was shut off. The coil stayed superconducting for about 90 min and then the entire coil became normal very uniformly. This result is consistent with the measured heat load of the solenoid of about 35 W. The results of the present tests indicate the excellent thermal stability of the solenoid.