Nicholas John Hadley

The inclusive production cross sections and transverse momentum distributions of ${K}^{*0}$ and ${{K}_{S}}^{0}$ mesons in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at a center-of-mass energy of 29 GeV have been measured by means of the time projection chamber detector in the PEP-4 experiment. The mean multiplicites are found to be 0.49 \ifmmode\pm\else\textpm\fi{} 0.04(stat.) \ifmmode\pm\else\textpm\fi{} 0.07(syst.) (${K}^{*0}+{\stackrel{-}{K}}^{*0}$) and 1.22 \ifmmode\pm\else\textpm\fi{} 0.03(stat.) \ifmmode\pm\else\textpm\fi{}0.15(syst.) (${K}^{0}+{\stackrel{-}{K}}^{0}$) per event.

Bose-Einstein correlations between like-sign pions have been investigated in ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ annihilation at \ensuremath{\surd}s =29 GeV using the Time Projection Chamber detector at the SLAC ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ storage ring PEP. The production rate of like-sign pion pairs with small relative momentum is found to be increased by more than 50% over the rate expected for uncorrelated production of pions. From the correlation length, a typical source radius of 0.65 fm is derived. Data are consistent with a spherical shape of the pion source. No dependence of radius or correlation strength on the event multiplicity is observed.

The inclusive production cross section of $\ensuremath{\Lambda}$, $\overline{\ensuremath{\Lambda}}$ in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at a c.m. energy of 29 GeV has been measured with the time-projection-chamber detector at PEP. The average $\ensuremath{\Lambda}$, $\overline{\ensuremath{\Lambda}}$ multiplicity has been measured to be 0.197 \ifmmode\pm\else\textpm\fi{} 0.012(stat.) \ifmmode\pm\else\textpm\fi{}0.017(syst.). $\ensuremath{\Lambda}\ensuremath{-}\overline{\ensuremath{\Lambda}}$ pairs have been observed in jets for the first time, and the average number of $\ensuremath{\Lambda}\ensuremath{-}\overline{\ensuremath{\Lambda}}$ pairs per event has been measured to be 0.042 \ifmmode\pm\else\textpm\fi{} 0.017 \ifmmode\pm\else\textpm\fi{} 0.014.

Correlations in rapidity space are presented for identified ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and ${K}^{\ifmmode\pm\else\textpm\fi{}}$ in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at 29-GeV c.m. energy. Short-range $\mathrm{KK}$ correlations indicate local flavor compensation in the hadronization process. Long-range $\mathrm{KK}$ and $\ensuremath{\pi}\ensuremath{\pi}$ correlations prove that the initial partons carry flavor. In addition, we observe significant $K\ensuremath{\pi}$ correlations as a result of heavy-quark decays.

We have studied the production of prompt muons in hadronic events from ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ annihilation at a center-of-mass energy of 29 GeV with the PEP4-TPC (Time Projection Chamber) detector. The muon p and ${p}_{t}$ distributions are well described by a combination of bottom- and charm-quark decays, with fitted semimuonic branching fractions of (15.2\ifmmode\pm\else\textpm\fi{}1.9\ifmmode\pm\else\textpm\fi{}1.2)% and (6.9\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\pm\else\textpm\fi{}1.1)%, respectively. The muon spectra imply hard fragmentation functions for both b and c quarks, with 〈z(b quark)〉=0.80\ifmmode\pm\else\textpm\fi{}0.05\ifmmode\pm\else\textpm\fi{}0.05 and 〈z(c quark)〉=0.60\ifmmode\pm\else\textpm\fi{}0.06\ifmmode\pm\else\textpm\fi{}0.04. We derive neutral-current axial-vector couplings of a(b quark)=-0.9\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\pm\else\textpm\fi{}0.3 and a(c quark)=1.5\ifmmode\pm\else\textpm\fi{}1.5\ifmmode\pm\else\textpm\fi{}0.5 from the forward-backward asymmetries.

The spatial resolution and response of the segmented cathode pads of the PEP-4 TPC have been measured with data taken at 8.5 atmospheres of 80% Argon-20% Methane gas with a 4kG magnetic field. The dependence of the spatial resolution and pad response on drift distance and track-anode crossing angle is presented.

Evidence for a narrow state decaying into an F meson and a photon has been obtained in e+e− annihilation events at 29-GeV c.m. energy. This state lies 139.5 ± 8.3(stat.) ± 9.7(syst.) MeV above the F-meson mass and is consistent with the expected F* meson. The F mesons are identified by a peak in the K+K−Kπ± mass at 1.948±0.028±0.010 GeV.Received 13 September 1984DOI:https://doi.org/10.1103/PhysRevLett.53.2465©1984 American Physical Society

We present here some results obtained with the LBL Time Projection Chamber (TPC) regarding the particle identification by the measurement of the ionization losses in the relativistic rise region. This includes the method of calibration using 55Fe sources, the measurement of the resolution using cosmic rays, which shows an equivalent K-π separation of 4.8 standard deviations at 3.5 GeV/c, and the preliminary results obtained with multihadronic events from e+e- annihilations.

We use the time-projection chamber detector to study mechanisms of baryon production in the central rapidity region of jets from ${e}^{+}{e}^{\ensuremath{-}}$ annihilation. On the basis of angular correlations between protons and antiprotons, we exclude the isotropic decay of heavy mesonic clusters as a dominant source of baryons at 95% confidence level. The diquark mechanisms used in string fragmentation models reproduce the data, provided that diquarks are formed in a two-step process which allows mesons to be produced in between the baryon and antibaryon.

The distribution of particles in three-jet events is compared with the predictions of three fragmentation models currently in use: the Lund string model, the Webber cluster model, and an independent fragmentation model. The Lund model and, to a certain extent, the Webber model provide reasonable descriptions of the data. The independent fragmentation model does not describe the distribution of particles at large angles with respect to the jet axes. The results provide evidence that the sources of hadrons are Lorentz boosted with respect to the overall c.m.Received 22 October 1984DOI:https://doi.org/10.1103/PhysRevLett.54.270©1985 American Physical Society

Production of $\ensuremath{\varphi}$ mesons in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at a center-of-mass energy of 29 GeV has been observed with the time-projection chamber detector at the PEP storage ring. The $\ensuremath{\varphi}$ production rate has been measured in the energy range $0.075<x<0.55$ ($x=\frac{2{E}_{\ensuremath{\varphi}}}{\sqrt{s}}$), giving 0.077\ifmmode\pm\else\textpm\fi{}0.012(stat)\ifmmode\pm\else\textpm\fi{}0.016(syst) $\ensuremath{\varphi}$'s per event. The average value of ${{p}_{t}}^{2}$ relative to the thrust axis is 1.0\ifmmode\pm\else\textpm\fi{}0.4 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$.

The top quark is the heaviest known elementary particle, and it is often seen as a window to search for new physics processes in particle physics. A large program to study the top-quark properties has been performed both at the Tevatron and LHC colliders by the D0, CDF, ATLAS and CMS experiments. The most recent results are discussed in this review.

We present a measurement of the top quark pair (tt¯) production cross section (σtt¯) in pp¯ collisions at a center-of-mass energy of 1.96 TeV using 230 pb−1 of data collected by the DØ detector at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), large missing transverse energy, and at least four jets, and extract the tt¯ content of the sample based on the kinematic characteristics of the events. For a top quark mass of 175 GeV, we measure σtt¯=6.7−1.3+1.4(stat)−1.1+1.6(syst)±0.4(lumi)pb, in good agreement with the standard model prediction.

Proton production in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at 29 GeV has been studied with the time projection chamber. Measurements of the dependence of proton fractions on momentum, transverse momentum with respect to the jet axis, hadron multiplicity, and event sphericity are reported. Our results are consistent with the assumption that primary baryons and mesons have similar production spectra, and indicate that protons provide more direct probes of underlying fragmentation phenomena than do pions.

From a study of $\ensuremath{\tau}$ decays using the Time Projection Chamber (TPC) detector at the SLAC ${e}^{+}{e}^{\ensuremath{-}}$ storage ring PEP, we have measured the one-, three-, and five-charged-particle inclusive branching fractions of the $\ensuremath{\tau}$ to be (85.2\ifmmode\pm\else\textpm\fi{}1.7)%, (14.8\ifmmode\pm\else\textpm\fi{}1.7)%, and 0.3%, respectively. Using particle identification by $\frac{\mathrm{dE}}{\mathrm{dx}}$ in the TPC we have searched for charged $K$ mesons in three-prong $\ensuremath{\tau}$ decays, and have set an upper limit on $B({\ensuremath{\tau}}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{K}^{\ifmmode\pm\else\textpm\fi{}}+2 \mathrm{c}\mathrm{h}\mathrm{a}\mathrm{r}\mathrm{g}\mathrm{e}\mathrm{d}+\mathrm{n}\mathrm{e}\mathrm{u}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{l}\mathrm{s})$ of 0.6%.

A Geiger-mode electromagnetic shower calorimeter has been constructed for PEP-4. Six trapezoidal modules cover 75% of 4π solid angle in a hexagonal array. Each module contains 40 sense wire planes between 0.25 radiation-length thick lead-laminates, and is divided electrically into submodules of 27 and 13 layers. Half-degree wide hodoscopic channels in projective geometry provide excellent spatial resolution. In each gap three stereo views using the sense wires as well as strips on both cathodes at ±60° to the wires provide good shower reconstruction capabilities in multi-track jet events. Calibration and data analysis procedures are outlined. The performance of the calorimeter in the measurement of Bhabha events and the reconstruction of π0's in jet events is in excellent agreement with Monte Carlo simulations. The π0 mass resolution is MeV (rms).

In a search for heavy charge-$\frac{4}{3}e$ particles produced in ${e}^{+}{e}^{\ensuremath{-}}$ collisions at a center-of-mass energy of 29 GeV, no candidate events were found in 22 ${\mathrm{pb}}^{\ensuremath{-}1}$ of data collected by the time projection chamber at PEP. Upper limits are established on the inclusive cross section for the production of charge-$\frac{4}{3}e$ particles in the mass range of 1-10 GeV/${\mathit{c}}^{2}$.

In order to reduce uncertainties in the comparison of jet cross section measurements, we are proposing a standard jet definition to be adopted for QCD measurements involving light quarks and gluons. This definition involves the use of cone in the {eta} -- {phi} metric with a radius of 0.7 units.

The PEP-4 hexagonal barrel calorimeter, with lead-laminate layers and 5×lOmm2 Geiger-mode discharge cells, has demonstrated excellent stability and uniformity in operation. The use of projective geometry in half degree-wide cathode strips at ±60 degrees to the sense wire channels provides excellent spatial resolution and reconstruction capability. The electronic noise-to-signal ratio without preamplification is sufficiently low that individual 50 pC Geiger discharges are accurately measured and used for energy calibration. Measurements made at 14.5 GeV e± beam energy have provided preliminary spectra of Bhabhas and of photon-photon invariant mass. The latter show that πo's can be reconstructed.

In a search for heavy Q=23e and Q=13e particles produced in e+e− collisions at a center-of-mass energy of 29 GeV, no candidate events were found in 77 pb−1 of data collected by the time projection chamber at PEP. Upper limits are established on the inclusive cross section for the production of Q=23e and Q=13 particles in the mass range 1-13 GeV/c2, improving upon previously established limits.Received 3 April 1984DOI:https://doi.org/10.1103/PhysRevLett.52.2332©1984 American Physical Society

A svstem of two cylindrical drift chambers has been designed and constructed to trigger the Time Projection Chamber and to assist in tracking and momentum reconstruction. Performance of these chambers has been studied with data collected from cosmic rays and actual e+e-collisions during recent experimental runs.

A large muon detection system has been constructed and is fully operational in the PEP 4 facility. It is more than 99.6% efficient. The system is rugged and reliable. It is possible to verify the integrity of all the chambers in a few minutes. Associated software for identifying muons has been written and is working.

We discuss the study of the top quark at future experiments and machines. Top's large mass makes it a unique probe of physics at the natural electroweak scale. We emphasize measurements of the top quark's mass, width, and couplings, as well as searches for rare or nonstandard decays, and discuss the complementary roles played by hadron and lepton colliders.

The Time Projection Chamber has operated in the PEP colliding beams at SLAC since January 1982. Its signal processing system, containing 16020 channels, has been calibrated and monitored using a computer-controlled test pulser system. We describe the test system and review measurements made with the system of signal processing electronics.

The authors discuss the study of the top quark at future experiments and machines. Top`s large mass makes it a unique probe of physics at the natural electroweak scale. They emphasize measurements of the top quark`s mass, width, and couplings, as well as searches for rare or nonstandard decays, and discuss the complementary roles played by hadron and lepton colliders.

We illustrate benefits to the U.S. economy and technological infrastructure of U.S. participation in accelerators overseas. We discuss contributions to experimental hardware and analysis and to accelerator technology and components, and benefits stemming from the involvement of U.S. students and postdoctoral fellows in global scientific collaborations. Contributed to the proceedings of the Snowmass 2013 Community Summer Study.

We have finished the third year of a three year grant cycle with the U.S. Department of Energy for which we were given a five month extension (U.S. D.O.E. Grant No. DEFG02-96ER41015). This document is the fi nal report for this grant and covers the period from November 1, 2010 to April 30, 2013. The Maryland program is administered as a single task with Professor Nicholas Hadley as Principal Investigator. The Maryland experimental HEP group is focused on two major research areas. We are members of the CMS experiment at the LHC at CERN working on the physics of the Energy Frontier. We are also analyzing the data from the Babar experiment at SLAC while doing design work and R&D towards a Super B experiment as part of the Intensity Frontier. We have recently joined the LHCb experiment at CERN. We concluded our activities on the D experiment at Fermilab in 2009.

We illustrate benefits to the U.S. economy and technological infrastructure of U.S. participation in accelerators overseas. We discuss contributions to experimental hardware and analysis and to accelerator technology and components, and benefits stemming from the involvement of U.S. students and postdoctoral fellows in global scientific collaborations. Contributed to the proceedings of the Snowmass 2013 Community Summer Study.

We illustrate benefits to the U.S. economy and technological infrastructure of U.S. participation in accelerators overseas. We discuss contributions to experimental hardware and analysis and to accelerator technology and components, and benefits stemming from the involvement of U.S. students and postdoctoral fellows in global scientific collaborations. Contributed to the proceedings of the Snowmass 2013 Community Summer Study.

Abstract We present the essential features of the design of the multiwire proportional detectors used in the PEP-4 Time Projection Chamber

The NA34 (HELIOS) calorimeter has measured e/{pi} {congruent} 1.1 in a uranium/liquid argon calorimeter with a shaping time of 135 nsec. Lead may be a viable alternative, but e/{pi} must first be measured at fast shaping times in lead. We re preparing to measure e/{pi} at momenta ranging from 0.5 to 20 GeV/c and with shaping times of 50, 100 and 150 nsec.

The D0 collaboration reports on the observation of top quark in p{bar p} collisions at {radical}{bar s} = 1.8 TeV at the Fermilab Tevatron. We measure the top quark mass to be 199{sub -21}{sup +19}(stat.){sub -21}{sup +14}(syst.) GeV/c{sup 2} and its production cross section to be 6.4 {+-} 2.2 pb. Our result is based on approximately 50 pb{sup -1} of data. We observe 17 events with an expected background of 3.8 {+-} 0.6 events. The probability of an upward fluctuation of the background to produce the observed signal is 2 x 10{sup -6} (equivalent to 4.6 standard deviations). The kinematic properties of the events are consistent with top quark decay, and the distribution of events across the seven decay channels is consistent with the Standard Model top quark branching fractions. We describe the analysis that led to the observation of the top quark as well as the properties of the top quark events.

A search for the lepton-flavor violating decay K/sup +/..--> pi../sup +/..mu../sup +/e/sup -/ has been performed. Measurements have also been made of the branching ratio and decay particle distributions for the decay K/sup +/..--> pi../sup +/e/sup -/. A description of the measurement technique, and preliminary results are presented. 6 refs., 5 figs.