N. Varelas

We report results of an electron-beam-dump search for neutral particles with masses in the range 1 to 15 MeV and lifetimes \ensuremath{\tau} between ${10}^{\mathrm{\ensuremath{-}}14}$ and ${10}^{\mathrm{\ensuremath{-}}10}$ s. No evidence was found for such an object. We fule out the existence of any 1.8-MeV pseudoscalar boson with \ensuremath{\tau}>8.2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}15}$ s and an absorption cross section in matter less than 1 mb per nucleon, and exclude \ensuremath{\tau}>1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}14}$ s were its cross section to equal 50 mb per nucleon. In conjunction with measurements of the electron's anomalous magnetic moment, this experiment shows that the narrow positron peaks observed in heavy-ion collisions at the Gessellschaft fu\ifmmode\ddot\else\textasciidieresis\fi{}r Schwerionenforschung are not due to an elementary pseudoscalar.

Increasing luminosity at the Fermilab Tevatron collider has led the D0 collaboration to make improvements to its detector beyond those already in place for Run IIa, which began in March 2001. One of the cornerstones of this Run IIb upgrade is a completely redesigned level-1 calorimeter trigger system. The new system employs novel architecture and algorithms to retain high efficiency for interesting events while substantially increasing rejection of background. We describe the design and implementation of the new level-1 calorimeter trigger hardware and discuss its performance during Run IIb data taking. In addition to strengthening the physics capabilities of D0, this trigger system will provide valuable insight into the operation of analogous devices to be used at LHC experiments.

Inclusive ${\ensuremath{\pi}}^{0}$ and direct-photon cross sections in the kinematic range $3.5<{p}_{T}<12\mathrm{GeV}/c$ with central rapidities ( ${y}_{\mathrm{cm}}$) are presented for $530\mathrm{and}800\mathrm{GeV}/c$ proton beams and a $515\mathrm{GeV}/c$ ${\ensuremath{\pi}}^{\ensuremath{-}}$ beam incident on Be targets. Current next-to-leading-order perturbative QCD calculations fail to adequately describe the data for conventional choices of scales. Kinematic distributions from these hard scattering events provide evidence that the interacting partons carry significant initial-state parton transverse momentum ( ${k}_{T}$). Incorporating these ${k}_{T}$ effects phenomenologically greatly improves the agreement between calculations and the measured cross sections.

We present results from the initial run of Fermilab experiment E706. The data include incident π− and p beams at 500 GeV/c on Be and Cu targets, and span the kinematic ranges of transverse momentum and rapidity of 3.5≤pT≤10 GeV/c and −0.7≤yc.m.≤0.7, respectively. We have measured cross sections for π0 and direct-photon production, as well as the ηπ0 production ratio. From the data on Be and Cu, we have extracted the nuclear dependence of π0 production, parametrized as Aα. The cross sections are compared with next-to-leading-log QCD predictions for different choices of the QCD momentum scales and several sets of parton distribution functions.Received 28 December 1992DOI:https://doi.org/10.1103/PhysRevD.48.5©1993 American Physical Society

We present measurements of the production of high transverse momentum ${\ensuremath{\pi}}^{0}$ and $\ensuremath{\eta}$ mesons in $\mathrm{pp}$ and $p\mathrm{Be}$ interactions at 530 and $800\mathrm{GeV}/c.$ The data span the kinematic ranges: $1<{p}_{T}<10\mathrm{GeV}/c$ in transverse momentum and 1.5 units in rapidity. The inclusive ${\ensuremath{\pi}}^{0}$ cross sections are compared with next-to-leading order QCD calculations and to expectations based on a phenomenological parton-${k}_{T}$ model.

We have studied the production of J/ψ and ψ(2S) charmonium mesons in 515 GeV/c π−Be collisions in the Feynman-x range 0.1<xF<0.8. J/ψ mesons were detected via their decay into μ+μ−, and ψ(2S) mesons were studied in both the μ+μ− and J/ψπ+π− decay modes. J/ψ differential cross sections have been measured as functions of xF,pT2, and the cosine of the Gottfried-Jackson decay angle. We measure an inclusive J/ψ cross section of B(J/ψ→μ+μ−)σ(π−Be→J/ψ+X)/A= [9.3±0.1(stat)±1.1(syst)] nb/nucleon for J/ψ xF≳0.1. Our results are compared with those from other experiments performed at lower beam energies. We also measure the differential ψ(2S) cross section as a function of both xF and pT2, and a ψ(2S) inclusive cross section of B(ψ(2S)→J/ψπ+π−)σ(π−Be→ψ(2S)+X)/A=[7. 4±1.5(stat)±1.2(syst)] nb/nucleon for ψ(2S) xF≳0.1. The fraction of the inclusive J/ψ yield due to ψ(2S) meson decays is 0.083±0.017(stat) ±0.013(syst), and the observed ratio of ψ(2S) decay rates is B(ψ(2S)→J/ψπ+π−)/B(ψ(2S)→μ+μ−) =30.2±7.2(stat)±6.8(syst). We have searched for production of ‘‘hidden’’ charm resonances decaying into either J/ψπ±,ψ(2S)π±, or J/ψπ+π− systems, and report an upper limit of 3.1 nb/nucleon for the product of branching ratio and cross section for the recently reported enhancement at a J/ψπ+π− mass of 3.836 GeV/c2. © 1996 The American Physical Society.Received 11 September 1995DOI:https://doi.org/10.1103/PhysRevD.53.4723©1996 American Physical Society

We report on the production of J/psi mesons in 530 and 800 GeV/c proton - Be collisions in the Feynman-x range 0.0 < xf < 0.6. The J/psi mesons were detected via decays into opposite sign muon pairs. Differential distributions for J/psi production have been measured as functions of xf, pT^2, and cosine of the Gottfried-Jackson decay angle. These distributions are compared with results on J/psi production obtained in 515 GeV/c pion - Be collisions, measured by the same experiment, as well as with results from other experiments using incident protons.

We report on ${\ensuremath{\chi}}_{c1}$ and ${\ensuremath{\chi}}_{c2}$ production in the Feynman-x range $0.1&lt;{x}_{F}&lt;0.8$ in $515\mathrm{GeV}/c$ ${\ensuremath{\pi}}^{\ensuremath{-}}\mathrm{Be}$ collisions. The ${\ensuremath{\chi}}_{c}$ states are observed via their radiative decays into $J/\ensuremath{\psi}$'s. The resulting photons are detected either as showers in the electromagnetic calorimeter or after conversion in the target as ${e}^{+}{e}^{\ensuremath{-}}$ pairs in the tracking system. The fraction of $J/\ensuremath{\psi}$ production due to ${\ensuremath{\chi}}_{c1}$ and ${\ensuremath{\chi}}_{c2}$ decays is $0.443\ifmmode\pm\else\textpm\fi{}0.041\ifmmode\pm\else\textpm\fi{}0.035$. The ratio of the ${\ensuremath{\chi}}_{c1}$ to ${\ensuremath{\chi}}_{c2}$ cross section is $0.57\ifmmode\pm\else\textpm\fi{}0.18\ifmmode\pm\else\textpm\fi{}0.06$. Our results on $J/\ensuremath{\psi}$, $\ensuremath{\psi}(2S)$, and ${\ensuremath{\chi}}_{c}$ production indicate that $0.454\ifmmode\pm\else\textpm\fi{}0.044\ifmmode\pm\else\textpm\fi{}0.042$ of $J/\ensuremath{\psi}$'s are produced directly.

Measurements of the production of high transverse momentum direct photons by a $515\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/c$ ${\ensuremath{\pi}}^{\ensuremath{-}}$ beam and 530 and $800\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/c$ proton beams in interactions with beryllium and hydrogen targets are presented. The data span the kinematic ranges of $3.5&lt;{p}_{T}&lt;12\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/c$ in transverse momentum and 1.5 units in rapidity. The inclusive direct-photon cross sections are compared with next-to-leading-order perturbative QCD calculations and expectations based on a phenomenological parton-${k}_{T}$ model.

This report summarizes the work of the Energy Frontier New Physics working group of the 2013 Community Summer Study (Snowmass).

We report on a sample of $\frac{J}{\ensuremath{\psi}}$ mesons coming from secondary vertices, a characteristic of heavyquark decay, detected in the Fermilab Meson West spectrometer. Based on eight signal events in which a $\frac{J}{\ensuremath{\psi}}$ emerges from a secondary vertex occurring in an air-gap region, we obtain an inclusive $b\overline{b}$ cross section of 75 \ifmmode\pm\else\textpm\fi{} 31 \ifmmode\pm\else\textpm\fi{} 26 nb/nucleon. This result is compared to recent QCD predictions. We have also observed several events in the exclusive decay modes ${B}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}\frac{J}{\ensuremath{\psi}}+{K}^{\ifmmode\pm\else\textpm\fi{}}$ and ${B}^{0}\ensuremath{\rightarrow}\frac{J}{\ensuremath{\psi}}+{K}^{0*}$ in which the $B$ mass is fully reconstructed.

We report new measurements of inclusive direct photon production at high transverse momenta (${\mathit{p}}_{\mathit{T}}$) for ${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ and p interactions on Be at 500 GeV/c. The yields as a function of ${\mathit{p}}_{\mathit{T}}$ and rapidity (y) are in good agreement with expectations from next-to-leading-log QCD calculations employing recently extracted quark and gluon structure functions.

We describe the design, construction and operation of a straw-tube drift chamber consisting of four X and four Y planes of 16 mm diameter straw

We present results on the production of high transverse momentum charm mesons in collisions of 515 GeV/c negative pions with beryllium and copper targets. The experiment recorded a large sample of events containing high transverse momentum (pT) showers detected in an electromagnetic calorimeter. From these data, a sample of charm mesons has been reconstructed via their decay into the fully charged Kππ mode. A measurement of the single inclusive transverse momentum distribution of charged D mesons from 1 to 8 GeV/c is presented. An extrapolation of the measured differential cross section yields an integrated D± cross section of 11.4±2.7(stat)±3.3(syst) μb per nucleon for D± mesons with xF>0. The data are compared with expectations based upon next-to-leading-order perturbative QCD, as well as with results from PYTHIA. We also compare our integrated D± cross section with measurements from other experiments.Received 7 February 1997DOI:https://doi.org/10.1103/PhysRevD.56.1391©1997 American Physical Society

Abstract We report on the calibration and performance of a large lead liquid-argon electromagnetic calorimeter used by experiment E706 at Fermilab. The reconstructed π 0 mass was used to calibrate the energy response of the calorimeter. The systematic uncertainty in the linearity and uniformity of the mean-energy response of the calorimeter after calibration was found to be less than ±0.5% for the sample of data analyzed. Detector characteristics, including sampling fluctuations and position resolution, are discussed.

Abstract A charged particle spectrometer containing a 7120-channel silicon microstrip detector system, one component of Fermilab experiment E706 to study direct photon production in hadron-hadron collisions, was utilized in a run in which 6 million events were recorded. We describe the silicon system, provide early results of track and vertex reconstruction, and present data on the radiation damage to the silicon wafers resulting from the narrow high intensity beam.

We present results on the production of high transverse momentum pizero and eta mesons in pi-p and pi-Be interactions at 515 GeV/c. The data span the kinematic ranges 1 < p_T < 11 GeV/c in transverse momentum and -0.75 < y < 0.75 in rapidity. The inclusive pizero cross sections are compared with next-to-leading order QCD calculations and to expectations based on a phenomenological parton-k_T model.

We present results on the production of direct photons, pizero, and eta mesons on nuclear targets at large transverse momenta (p_T). The data are from 530 and 800 GeV/c proton beams and 515 GeV/c piminus beams incident upon copper and beryllium targets that span the kinematic range of 1.0 &lt; p_T &lt; 10 GeV/c at central rapidities.

We present the results of a study of hadronic jets produced in association with direct photons and π0's at large transverse momenta in π−Be and pBe collisions at 500 GeV/c. Using primarily charged particles to characterize the properties of the recoiling jets, we compare their fragmentation and angular distributions, and their correlation with the trigger particle, for both the γ and π0 event samples. We also compare the data with QCD calculations that incorporate current parton distribution functions.Received 9 September 1993DOI:https://doi.org/10.1103/PhysRevD.49.3106©1994 American Physical Society

We present new measurements of ${\ensuremath{\pi}}^{0}$ production at high transverse momenta (${p}_{T}$) for ${\ensuremath{\pi}}^{\ensuremath{-}}$ and $p$ interactions on Be and Cu targets at 500 GeV/c. The observed dependence of the yields as a function of ${p}_{T}$ and rapidity ($y$) is compared with expectations from leading-log QCD over a kinematic range in which the inclusive cross sections fall by more than 4 order of magnitude.

A study is presented of the sensitivity of potential future $pp$ colliders to quark compositeness. The analysis uses normalized dijet angular distributions compared to expectations from leading-order contact interaction models.

We report the method used to calibrate the energy response of the E706 Liquid Argon Electromagnetic Calorimeter to photons and electrons. The data used in the study included photons originating from π0 and η decays and electrons coming from photon conversions upstream of the analysis magnet. Electron momenta were independently measured by the tracking system. The process employed resulted in an overall systematic uncertainty in the calorimeter's energy scale of less than 0.5%.

We review the status of searches for the Standard Model (SM) Higgs boson from the CDF and DØ experiments using a Run II data sample of ≈ 400 pb -1 pp collisions at center of mass energy of 1.96 TeV at the Fermilab Tevatron.No evidence for signal is found and updated limits on the SM Higgs production cross section times branching ratio are presented.Studies of W and Z bosons produced in association with jets (background processes to SM Higgs production) are also discussed.

We present a new measurement of the mass of the top quark using lepton + jets ttbar events collected by the DO experiment in Run I of the Fermilab Tevatron Collider. The mass is extracted through a comparison of each event with a leading-order matrix element that depends on the top quark mass. The result is M_t=180.1 +/- 3.6 (stat) +/- 3.9 (sys) GeV/c^2. Combining this improved measurement with our previous value from dilepton channels yields the new DO result M_t=179.0 +/- 3.5 (stat) +/- 3.8 (sys) GeV/c^2.

With increasing Tevatron luminosity, efficient triggers that meet the bandwidth limitations of the experiment's data acquisition system become more and more difficult to construct. To meet these challenges, the DOslash experiment has significantly enhanced its triggering capabilities. A major component of this upgrade is a completely re-designed Level-1 calorimeter trigger (L1Cal). This new system uses novel architecture and algorithms to maintain acceptable background rejection while preserving or even improving signal efficiency at the highest luminosities foreseen. We describe interesting features of the L1Cal and give highlights from its first few months of operation.

We present recent results from the D0 experiment on W and Z boson production using {approx} 50 pb{sup -1} of Run II data recorded at the center of mass energy of 1.96 TeV at the Fermilab Tevatron. Initial studies of W/Z + 2 jets production that are relevant to Higgs searches are also discussed.

We review the status of searches for the Standard Model (SM) Higgs boson from the CDF and DO experiments using a Run II data sample of… 400 pb i1 p p collisions at center of mass energy of 1:96 TeV at the Fermilab Tevatron. No evidence for signal is found and updated limits on the SM Higgs production cross section times branching ratio are presented. Studies of W and Z bosons produced in association with jets (background processes to SM Higgs production) are also discussed.

The authors report on a new measurement of the rapidity dependence of the inclusive jet production cross section in p{bar p} collisions at {radical}s = 1:8 TeV using 92 pb{sup {minus}1} of data collected by the DO detector at the Tevatron collider. The differential cross sections, , are presented as a function of jet transverse energy (E{sub T}) in five pseudorapidity ({eta}) intervals, up to {vert_bar}{eta}{vert_bar} = 3, significantly extending previous measurements beyond {vert_bar}{eta}{vert_bar} = 0.7. They also present recent results on the ratio of central ({vert_bar}{eta}{vert_bar} < 0.5) inclusive cross sections from two center-of-mass energies, 0.63 TeV and 1.8 TeV, as a function of jet x{sub T}. Experimental results are compared to next-to-leading order QCD predictions.

We present a status report of a variety of projects related to heavy quark production and parton distributions for the Tevatron Run II.

The main focus of this working group was to investigate the different issues associated with the development of quantitative tools to estimate parton distribution functions uncertainties. In the conclusion, we introduce a Manifesto that describes an optimal method for reporting data.

Recent experimental results on color coherence phenomena from e+e-, ep, and ppbar collisions are presented. The data are compared to analytic perturbative QCD calculations based on the modified leading logarithm approximation and the local parton hadron duality hypothesis.

Inclusive {pi}{sup 0} and direct-photon cross sections in the kinematic range 3.5{lt}p{sub T}{lt}12 GeV/c with central rapidities (thinspy{sub cm} ) are presented for 530 and 800 GeV/c proton beams and a 515 GeV/c {pi}{sup {minus}} beam incident on Be targets. Current next-to-leading-order perturbative QCD calculations fail to adequately describe the data for conventional choices of scales. Kinematic distributions from these hard scattering events provide evidence that the interacting partons carry significant initial-state parton transverse momentum (k{sub T} ). Incorporating these k{sub T} effects phenomenologically greatly improves the agreement between calculations and the measured cross sections. {copyright} {ital 1998} {ital The American Physical Society}

We present recent results on jet production, dijet angular distributions, W + Jets, and color coherence from p- collisions at √s = 1.8 TeV at the Fermilab Tevatron Collider using the DO detector. The data are compared to perturbative QCD calculations or to predictions of parton shower based Monte Carlo models.

Results from a search for new particles decaying to dijets in fi = 1.8 TeV pp collisions using the DO 1992-93 and 1994-95 data samples (104 pb-1) are presented. We exclude at the 95% confidence level the production of excited quarks with masses below 725 GeV/ c2, an additional standard model W boson with masses between 340 and 680 GeV/ c2 and an additional standard model 2 boson with masses between 365 and 615 GeV/c2. *Submitted to the International Europhysics Conference on High Energy Physics, August 19 26, 1997, Jerusalem, Israel.

We present results on the production of high transverse momentum charm mesons in collisions of 515 GeV/c negative pions with beryllium and copper targets. The experiment recorded a large sample of events containing high transverse momentum (p{sub T}) showers detected in an electromagnetic calorimeter. From these data, a sample of charm mesons has been reconstructed via their decay into the fully charged K{pi}{pi} mode. A measurement of the single inclusive transverse momentum distribution of charged D mesons from 1 to 8 GeV/c is presented. An extrapolation of the measured differential cross section yields an integrated D{sup {plus_minus}} cross section of 11.4{plus_minus}2.7(stat){plus_minus}3.3(syst) {mu}b per nucleon for D{sup {plus_minus}} mesons with x{sub F}{gt}0. The data are compared with expectations based upon next-to-leading-order perturbative QCD, as well as with results from PYTHIA. We also compare our integrated D{sup {plus_minus}} cross section with measurements from other experiments. {copyright} {ital 1997} {ital The American Physical Society}

Abstract

We present recent results on jet production, dijet angular distributions, W+ Jets, and color coherence from p{anti p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron Collider using the D0 detector. The data are compared to perturbative QCD calculations or to predictions of parton shower based Monte Carlo models.

We present recent results on measurements of the transverse momentum distribution of W and Z bosons, the angular distribution of electrons from W decays, and on color coherence effects in W+jets events from p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron Collider. The data are compared to perturbative QCD calculations.

We present results on measurements of jet shapes, color coherence, and topology of multijet events from {ital p}{ital {anti p}} collisions at {radical}s = TeV at the Fermilab Tevatron collider using the CDF and D{null} detectors. The data are compared to next-to-leading order QCD calculations, or to predictions of parton shower based Monte Carlo models.

We present two QCD studies based on data collected by the DO/ detector during the 1992–1993 run and data recorded by the CDF detector during the 1988–1989 run of the Fermilab Tevatron pp̄ collider at a center of mass energy of √s=1.8 TeV. The first study by the DO/ collaboration presents preliminary results on jet‐jet angular decorrelation as a function of rapidity separation. This measurement is compared to HERWIG shower‐level and JETRAD NLO parton‐level Monte Carlo simulations. Data are also compared to predictions based on the techniques of Balitsky, Fadin, Kuraev, and Lipatov to resum soft gluon emissions which are expected to cause decorrelation of the produced jets. The second study demonstrates initial‐to‐final state color coherence effects by measuring the spatial correlations between soft and hard jets in multijet events. Both CDF results and DO/ preliminary measurements are presented and compared to several Monte Carlo simulations with different color coherence implementations. The DO/ data, which include both central and forward jets, are also compared to the predictions of JETRAD Monte Carlo.

We report on a sample of [ital J]/[psi] mesons coming from secondary vertices, a characteristic of heavy-quark decay, detected in the Fermilab Meson West spectrometer. Based on eight signal events in which a [ital J]/[psi] emerges from a secondary vertex occurring in an air-gap region, we obtain an inclusive [ital b[bar b]] cross section of 75[plus minus]31[plus minus]26 nb/nucleon. This result is compared to recent QCD predictions. We have also observed several events in the exclusive decay modes [ital B][sup [plus minus]][r arrow][ital J]/[psi]+[ital K][sup [plus minus]] and [ital B][sup 0][r arrow][ital J]/[psi]+[ital K][sup 0*] in which the [ital B] mass is fully reconstructed.

We are studying production of χc states in 530 GeV/c π− interactions with several targets. χc mesons are observed in the mode (χ→J/ψ+γ). Only photons that converted to e+e− pairs are used in the reconstruction of the χc mesons. Preliminary analysis shows that the fraction of observed J/ψs coming from χc radiative decays is 0.44±0.09±0.08, and that the relative production rate of χc1 to χc2 is 1.3±0.6.

The author presents two QCD studies based on data collected by the D(0) detector during the 1992-1993 run and data recorded by the CDF detector during the 1988-1989 run of the Fermilab Tevatron p{bar p} collider at a center of mass energy of {radical}s = 1.8 TeV. The first study by the D(0) collaboration presents preliminary results on jet-jet angular decorrelation as a function of rapidity separation. This measurement is compared to HERWIG shower-level and JETRAD NLO parton-level Monte Carlo simulations. Data are also compared to predictions based on the techniques of Balitsky, Fadin, Kuraev, and Lipatov to resum soft gluon emissions which are expected to cause decorrelation of the produced jets. The second study demonstrates initial-to-final state color coherence effects by measuring spatial correlations between soft and hard jets in multijet events. Both CDF results and D(0) preliminary measurements are presented and compared to several Monte Carlo simulations with different color coherence implementations. The D(0) data, which include both central and forward jets, are also compared to the predictions of JETRAD Monte Carlo.

The inclusive $\pi^0$ cross section in 520 GeV/c $\pi^-$ Be and $\pi^-$ Cu interactions has been measured as a function of transverse momentum and rapidity, using the E706 spectrometer at FNAL. The production of $\pi^0$ s was studied using = 5.2 events/pb of $\pi^-$ Be data and = 0.84 events/pb of $\pi^-$ Cu data collected during the 1990 run of the E706 experiment. This data sample represents an order of magnitude increase in statistics over the data recorded during the initial run of the experiment in 1988. The $\pi^0$ decay photons were detected by a finely segmented liquid argon electromagnetic calorimeter. The $\pi^0$ cross section was measured for transverse momenta between 3.5 and 10 GeV/c and rapidities between -0.75 and 0.75. From the data on Be and Cu, we have extracted the nuclear dependence of $\pi^0$ production. The measurements are compared with earlier results, as well as with recent next-to-leading-log calculations from Quantum Chromodynamics (QCD).

We report the method used to calibrate the energy response of the E706 Liquid Argon Electromagnetic Calorimeter to photons and electrons. The data used in the study included photons originating from π0 and η decays and electrons coming from photon conversions upstream of the analysis magnet. Electron momenta were independently measured by the tracking system. The process employed resulted in an overall systematic uncertainty in the calorimeter's energy scale of less than 0.5%.