P. E. Karchin

We measure forward cross sections for production of ${D}^{+}$, ${D}^{0}$, ${D}_{s}$, ${D}^{*+}$, and ${\ensuremath{\Lambda}}_{c}$ in collisions of ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${K}^{\ifmmode\pm\else\textpm\fi{}}$, and $p$ on a nuclear target. Production induced by different beam particles is found to be the same within statistics. Strange and baryonic final states are seen to contribute appreciably to the total charm cross section, which our measurements indicate is larger than but consistent with QCD predictions. The energy dependence mapped out by these and previous measurements is consistent with theory. Leading-particle asymmetry measurements for $K$ and $p$-induced charm production are also presented.

A leading charm meson is one with longitudinal momentum fraction, ${\mathit{x}}_{\mathit{F}}$>0, whose light quark (or antiquark) is of the same type as one of the quarks in the beam particles. We report on the production asymmetry, A=[\ensuremath{\sigma}(leading-\ensuremath{\sigma}(nonleading)]/[\ensuremath{\sigma}(leading)+\ensuremath{\sigma}(nonleading)] as a function of ${\mathit{x}}_{\mathit{F}}$. The data consist of 1500 fully reconstructed ${\mathit{D}}^{\ifmmode\pm\else\textpm\fi{}}$ and ${\mathit{D}}^{\mathrm{*}\ifmmode\pm\else\textpm\fi{}}$ decays in Fermilab experiment E 769. We find a significant asymmetry for the production of charm quarks is not expected in perturbative quantum chromodynamics.

We present a study of ${D}^{0}$ mixing using events of the type ${D}^{\mathrm{*}+}$\ensuremath{\rightarrow}${\ensuremath{\pi}}^{+}$${D}^{0}$, with ${D}^{0}$\ensuremath{\rightarrow}${K}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ and ${D}^{0}$\ensuremath{\rightarrow}${K}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$${\ensuremath{\pi}}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$. The decay time is used to separate mixing from doubly Cabibbo-suppressed decays. We observe no evidence for mixing in either mode. Combining the results from the two decay modes, we find ${r}_{M}$=0.0005 \ifmmode\pm\else\textpm\fi{}0.0020 or ${r}_{M}$0.0037 at the 90% confidence level, where ${r}_{M}$ is the ratio of wrong-sign decays from mixing to right-sign decays. We also present limits on doubly Cabibbo-suppressed decays and consider the effect of possible interference.

Using the Tagged Photon Spectrometer and a high-energy photon beam, we have searched for excited states of charm in Fermilab experiment E691. We have found evidence for a state of mass 2459±3 (stat.) ±2 (syst.) MeV/c2 and width 20±10±5 MeV/c2 which decays to D+π−. The fraction of D+ coming from D**0(2459) is 0.07±0.02±0.02. We also confirm the D**0(2420)→D*+π− decay observed previously in e+e− experiments and present evidence for its charged counterpart.Received 22 September 1988DOI:https://doi.org/10.1103/PhysRevLett.62.1717©1989 American Physical Society

We measure the relative cross sections for D mesons produced in interactions of ${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ and ${\mathrm{\ensuremath{\pi}}}^{+}$ beams with targets of Be, Cu, Al, and W. The measurement is based on 1400 fully reconstructed decays of the types ${\mathit{D}}^{0}$\ensuremath{\rightarrow}${\mathit{K}}^{\mathrm{\ensuremath{-}}}$${\mathrm{\ensuremath{\pi}}}^{+}$, ${\mathit{D}}^{+}$\ensuremath{\rightarrow}${\mathit{K}}^{\mathrm{\ensuremath{-}}}$${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{+}$, and charge conjugates. We find that the cross section for the production of both neutral and charged D's by either ${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ or ${\mathrm{\ensuremath{\pi}}}^{+}$ is well fitted by the form ${\mathit{A}}^{\mathrm{\ensuremath{\alpha}}}$ where A is the atomic mass and \ensuremath{\alpha}=1.00\ifmmode\pm\else\textpm\fi{}0.05\ifmmode\pm\else\textpm\fi{}0.02, where the errors are statistical and systematic, respectively. There is no significant dependence of \ensuremath{\alpha} on the transverse or longitudinal momentum of the D meson or on the charge of either the incident pion or the produced D mesons.

We have measured the lifetimes of the ${D}^{0}$, ${D}^{+}$, and ${D}_{s}^{+}$ mesons which were produced by a high-energy photon beam incident on beryllium. Using the Fermilab Tagged Photon Spectrometer with a silicon-microstrip vertex detector we have collected ${10}^{8}$ events from which we have extracted about 4200 ${D}^{0}$ decays in the ${K}^{\mathrm{\ensuremath{-}}}$${\ensuremath{\pi}}^{+}$ and ${K}^{\mathrm{\ensuremath{-}}}$${\ensuremath{\pi}}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$${\ensuremath{\pi}}^{+}$ modes, 3000 ${D}^{+}$ into the ${K}^{\mathrm{\ensuremath{-}}}$${\ensuremath{\pi}}^{+}$${\ensuremath{\pi}}^{+}$ channel, and a total of 230 ${D}_{s}^{+}$ into \ensuremath{\varphi}${\ensuremath{\pi}}^{+}$ and K${\ifmmode\bar\else\textasciimacron\fi{}}^{\mathrm{*}0}$${K}^{+}$. From an analysis of these events we have determined the lifetimes for the ${D}^{0}$, ${D}^{+}$, and ${D}_{s}^{+}$ to be 0.422\ifmmode\pm\else\textpm\fi{}0.008\ifmmode\pm\else\textpm\fi{}0.010, 1.090\ifmmode\pm\else\textpm\fi{}0.030\ifmmode\pm\else\textpm\fi{}0.025, and 0.47\ifmmode\pm\else\textpm\fi{}0.04\ifmmode\pm\else\textpm\fi{}0.02 psec, respectively.

We present results on the photoproduction of 10 000 charmed particles from the ${10}^{8}$ recorded triggers of Fermilab experiment E691. The total cross section for the photoproduction of ${D}^{0}$ and ${D}^{+}$ particles (and antiparticles) for ${x}_{F}>0.2$ is measured to be 3.88\ifmmode\pm\else\textpm\fi{}0.06\ifmmode\pm\else\textpm\fi{}0.40 \ensuremath{\mu}b/Be nucleus at $〈{E}_{\ensuremath{\gamma}}〉=145$ GeV. We have also measured the relative production of different charmed particles, their ${p}_{T}^{2}$ and ${x}_{F}$ distributions, and the energy dependence of the total charm cross section. The mean ${p}_{T}^{2}$ is 1.16\ifmmode\pm\else\textpm\fi{}0.04 Ge${\mathrm{V}}^{2}$/${\mathit{c}}^{2}$ and the ratio of charm cross sections at 200 and 100 GeV is 1.96\ifmmode\pm\else\textpm\fi{}0.24. Results of fits to the ${x}_{F}$ distribution are also reported.

We measure the differential cross sections with respect to Feynman $x$ ( ${x}_{F}$) and transverse momentum ( ${p}_{T}$) for $\ensuremath{\pi}$, $K$, and $p$-induced charm meson production using fully reconstructed ${D}^{+}$, ${D}^{0}$, and ${D}_{s}$ decays. The shapes of these cross sections are compared to the theoretical predictions for charm quark production of next-to-leading order perturbative QCD using modern parametrizations of the pion and nucleon parton distributions. We observe the differences expected in production induced by projectiles with different gluon distributions, harder distributions being indicated for mesons than for protons.

Using a silicon vertex detector, we measure the charged particle pseudorapidity distribution over the range 1.5 to 5.5 using data collected from PbarP collisions at root s = 630 GeV. With a data sample of 3 million events, we deduce a result with an overall normalization uncertainty of 5%, and typical bin to bin errors of a few percent. We compare our result to the measurement of UA5, and the distribution generated by the Lund Monte Carlo with default settings. This is only the second measurement at this level of precision, and only the second measurement for pseudorapidity greater than 3.

We measure the differential cross section with respect to Feynman-x (xF) and transverse momentum (PT) for charm meson production using targets of Be, Al, Cu, and W. In the range 0.1<xF<0.7, dσ/dxF is well fit by the form (1-xF)n with n=3.9±0.3. The difference between n values for D− and D+ is 1.1±0.7. However, we find an asymmetry of 0.18±0.06 favoring the production of D− compared to D+. In the lower PT range, <2 GeV, dσ/dP2T is well fit by the form exp(-b×P2T) with b=1.03±0.06 GeV−2, while in the higher PT range, 0.8 to 3.6 GeV, it is well fit by the form exp(-b’×PT) with b’=2.76±0.08 GeV−1. The shape of the differential cross section has no significant dependence on atomic mass of the target material.Received 8 October 1992DOI:https://doi.org/10.1103/PhysRevLett.69.3147©1992 American Physical Society

Results are presented on ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p$, ${K}^{\ifmmode\pm\else\textpm\fi{}}p$, and ${p}^{\ifmmode\pm\else\textpm\fi{}}p$ elastic scattering measured with an apparatus having acceptance of $0.5&lt;\ensuremath{-}t&lt;2.5$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ and $0.9&lt;\ensuremath{-}t&lt;11$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ at 100 and 200 GeV/c, respectively. A diffractionlike dip is seen for the first time in the ${\ensuremath{\pi}}^{\ensuremath{-}}p t$ distribution at $\ensuremath{-}t=4$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. All meson-proton cross sections are found to be similar in the range $1&lt;\ensuremath{-}t&lt;2.5$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$, although some small systematic differences are observed. Cross sections for $\mathrm{pp}$ and $\stackrel{-}{p}p$ are compared with previous data.

Abstract Large apecture forward spectrometers with planar geometry perpendicular to the beam line are the natural detectors to accomodate the expected forward peaking of Beauty particle production at high energy hadron colliders. We have designed, built and tested a prototype planar silicon strip vertex detector for triggering such a spectrometer system. The test system consisted of 43 000 channels, configured in six planes, each with four quadrants, perpendicular to the beam line and installed inside the SPS-collider vacuum pipe at the center of an interaction region. Events recorded with the rf shield of the silicon system 1.5 mm from the circulating beams show negligible event-unrelated background.

Results are presented on the measurement of 200-GeV/c ${\ensuremath{\pi}}^{\ensuremath{-}}p$ elastic scattering at $\ensuremath{-}t$ from 0.8 to 11 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. As $\ensuremath{-}t$ is increased, $\frac{d\ensuremath{\sigma}}{\mathrm{dt}}$ falls by \ensuremath{\sim}6 decades to a prominent dip at 4 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$, followed by a second maximum and than a slow decrease with increasing $\ensuremath{-}t$.

At present, part of the forward RPC muon system of the CMS detector at the CERN LHC remains uninstrumented in the high-\eta region. An international collaboration is investigating the possibility of covering the 1.6 < |\eta| < 2.4 region of the muon endcaps with large-area triple-GEM detectors. Given their good spatial resolution, high rate capability, and radiation hardness, these micro-pattern gas detectors are an appealing option for simultaneously enhancing muon tracking and triggering capabilities in a future upgrade of the CMS detector. A general overview of this feasibility study will be presented. The design and construction of small (10\times10 cm2) and full-size trapezoidal (1\times0.5 m2) triple-GEM prototypes will be described. During detector assembly, different techniques for stretching the GEM foils were tested. Results from measurements with x-rays and from test beam campaigns at the CERN SPS will be shown for the small and large prototypes. Preliminary simulation studies on the expected muon reconstruction and trigger performances of this proposed upgraded muon system will be reported.

We have built a working system of silicon microstrip detectors that achieves a single plane resolution better than 19 microns, a track efficiency close to 100% for normal incidence, and a noise rate of less than 10-3. This detector system meets the requirements for a "microvertex" detector in a high rate, fixed target environment.

Gas Electron Multipliers (GEM) are a proven position sensitive gas detector technology which nowadays is becoming more widely used in High Energy Physics. GEMs offer an excellent spatial resolution and a high particle rate capability, with a close to 100% detection efficiency. In view of the high luminosity phase of the CERN Large Hadron Collider, these aforementioned features make GEMs suitable candidates for the future upgrades of the Compact Muon Solenoid (CMS) detector. In particular, the CMS GEM Collaboration proposes to cover the high-eta region of the muon system with large-area triple-GEM detectors, which have the ability to provide robust and redundant tracking and triggering functions. In this contribution, after a general introduction and overview of the project, the construction of full-size trapezoidal triple-GEM prototypes will be described in more detail. The procedures for the quality control of the GEM foils, including gain uniformity measurements with an x-ray source will be presented. In the past few years, several CMS triple-GEM prototype detectors were operated with test beams at the CERN SPS. The results of these test beam campaigns will be summarised.

Silicon pixel detectors allow measurement of charm and bottom decays, which have mean rest-frame decay lengths in the range 60–360 μm. Because of the high particle density which can be accommodated by detectors with pixel size 30 μm × 30 μm, direct measurement of decay paths should be possible in future fixed-target experiments. At high energy hadron colliders like the SSC and LHC and at e+e− colliders operating at the Z0 resonance the two particle separation will be of order 70 μm at the inner barrel. Such a high track density can best be accommodated with pixel detectors. A prototype readout chip for a pixel detector has been submitted for fabrication by an SSC R&D collaboration. This chip contains a random access array of 32 × 64 cells of dimension 45 × 150 μm. Each cell has analog and digital storage. The performance goal is 300 electrons rms noise at 20°C and full charge collection in 50 ns.

The international CMS GEM collaboration is studying the feasibility of upgrading the CMS forward muon system by adding layers of triple GEM based detectors. After successful tests of small size tripe-GEM chambers in the period of 2010-2011, the collaboration has designed, built and tested full-size GEM chambers for the upgrade purpose. We report on results from test beam and simulation that were conducted to study the performance of the GEM chambers.

In order to cope with the harsh environment expected from the high luminosity LHC, the CMS forward muon system requires an upgrade. The two main challenges expected in this environment are an increase in the trigger rate and increased background radiation leading to a potential degradation of the particle ID performance. Additionally, upgrades to other subdetectors of CMS allow for extended coverage for particle tracking, and adding muon system coverage to this region will further enhance the performance of CMS. Following an extensive R&D program, CMS has identified triple-foil gas electron multiplier (GEM) detectors as a solution for the first muon station in the region 1.6<|η|<2.2, while continuing R&D is ongoing for additional regions.

The CMS muon system in the region with 2.03<|η|<2.82 is characterized by a very harsh radiation environment which can generate hit rates up to 144 kHz/cm2 and an integrated charge of 8 C/cm2 over ten years of operation. In order to increase the detector performance and acceptance for physics events including muons, a new muon station (ME0) has been proposed for installation in that region. The technology proposed is Triple—Gas Electron Multiplier (Triple-GEM), which has already been qualified for the operation in the CMS muon system. However, an additional set of studies focused on the discharge probability is necessary for the ME0 station, because of the large radiation environment mentioned above. A test was carried out in 2017 at the Cern High energy AcceleRator Mixed (CHARM) facility, with the aim of giving an estimation of the discharge probability of Triple-GEM detectors in a very intense radiation field environment, similar to the one of the CMS muon system. A dedicated standalone Geant4 simulation was performed simultaneously, to evaluate the behavior expected in the detector exposed to the CHARM field. The geometry of the detector has been carefully reproduced, as well as the background field present in the facility. This paper presents the results obtained from the Geant4 simulation, in terms of sensitivity of the detector to the CHARM environment, together with the analysis of the energy deposited in the gaps and of the processes developed inside the detector. The discharge probability test performed at CHARM will be presented, with a complete discussion of the results obtained, which turn out to be consistent with measurements performed by other groups.

Gas Electron Multiplier (GEM) technology is being considered for the forward muon upgrade of the CMS experiment in Phase 2 of the CERN LHC. Its first implementation is planned for the GE1/1 system in the 1.5 <| η |< 2.2 region of the muon endcap mainly to control muon level-1 trigger rates after the second long LHC shutdown. A GE1/1 triple-GEM detector is read out by 3,072 radial strips with 455 µrad pitch arranged in eight η-sectors. We assembled a full-size GE1/1 prototype of 1m length at Florida Tech and tested it in 20–120 GeV hadron beams at Fermilab using Ar/CO2 70∶30 and the RD51 scalable readout system. Four small GEM detectors with 2-D readout and an average measured azimuthal resolution of 36 µrad provided precise reference tracks. Construction of this largest GEM detector built to-date is described. Strip cluster parameters, detection efficiency, and spatial resolution are studied with position and high voltage scans. The plateau detection efficiency is [97.1 ± 0.2 (stat)]%. The azimuthal resolution is found to be [123.5 ± 1.6 (stat)] µrad when operating in the center of the efficiency plateau and using full pulse height information. The resolution can be slightly improved by ∼ 10 µrad when correcting for the bias due to discrete readout strips. The CMS upgrade design calls for readout electronics with binary hit output. When strip clusters are formed correspondingly without charge-weighting and with fixed hit thresholds, a position resolution of [136.8 ± 2.5 stat] µrad is measured, consistent with the expected resolution of strip-pitch/equation µrad. Other η-sectors of the detector show similar response and performance.

A multi-institutional collaboration is investigating the possibility of enhancing muon tracking and triggering capabilities in the small-angle region 1.6 < |η| < 2.1 of the CMS experiment at the LHC by instrumenting the end-cap muon system with large-area gas electron multiplier (GEM) detectors.A first trapezoidal prototype triple-GEM detector of size 1 m × 0.5 m was built and operated successfully in a test beam at CERN in October 2010.Front-end readout boards utilizing the "VFAT" chip are mounted in a regular array directly on the chambers.High voltage is provided by a compact divider board implemented with surface mount components.A tracker equipped with small GEM detectors was used to precisely measure the hit position in the large-area detector.A spatial resolution of 290 µm was measured in a region with average strip pitch of 1.1 mm, and ~98% hit efficiency was achieved at full operating voltage.An additional prototype chamber is constructed and will undergo beam tests this summer with operation in a 3 T magnetic field.

Gas Electron Multipliers (GEM) are an interesting technology under consideration for the future upgrade of the forward region of the CMS muon system, specifically in the 1.6 <; |η| <; 2:4 endcap region. With a sufficiently fine segmentation GEMs can provide precision tracking as well as fast trigger information. The main objective is to contribute to the improvement of the CMS muon trigger. The construction of large-area GEM detectors is challenging both from the technological and production aspects. In view of the CMS upgrade we have designed and built the largest full-size Triple-GEM muon detector, which is able to meet the stringent requirements given the hostile environment at the high-luminosity LHC. Measurements were performed during several test beam campaigns at the CERN SPS in 2010 and 2011. The main issues under study are efficiency, spatial resolution and timing performance with different inter-electrode gap configurations and gas mixtures. In this paper results of the performance of the prototypes at the beam tests will be discussed.

We have searched for the exclusive semileptonic decay modes D+→K¯ππe+νe and D+→K¯*πe+νe in the data from the Fermilab photoproduction experiment E691. With good sensitivity, we observe no signals in the channels D+→K−π+π0e+νe and D+→K¯0π+π−e+νe, and set upper limits of B(D+→all K¯*πe+νe)<1.2% and B(D+→all K¯ππe+νe)<0.9%, at the 90% confidence level. (For these limits we use isospin invariance to extract limits which include all charge states.) These modes are expected to be the most common semileptonic decays next to the dominant K¯e+νe and K¯*e+νe, but the observed limits represent a small fraction of the inclusive semileptonic branching ratio of (17.0±1.9±1.7)%.Received 29 October 1991DOI:https://doi.org/10.1103/PhysRevD.45.R2177©1992 American Physical Society

We report results from Fermilab experiment E769 on the differential cross sections of D*± charm vector mesons with respect to Feynman-x (xF) and transverse momentum (PT), and on the atomic mass dependence of the production. The D∗ mesons were produced by a 250 GeV π beam on a target of Be, Al, Cu, and W foils. The dσdxF distribution is fit by the form ((1−xF)n) with n=3.5±0.3±0.1, the dσdP2T distribution by exp(−b×P2T) with b=0.70±0.07±0.04 GeV−2, and the cross section A dependence by Aα with α=1.00±0.07±0.02. These results are compared to the equivalent parameters for the production of pseudoscalar D0 and D± charm mesons.Received 10 September 1993DOI:https://doi.org/10.1103/PhysRevD.49.R4317©1994 American Physical Society

Antiproton-proton elastic scattering has been measured at 100 GeV/c for $0.5&lt;\ensuremath{-}t&lt;2.5$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ and at 200 GeV/c for $0.9&lt;\ensuremath{-}t&lt;4$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. The data show that the $\ensuremath{-}t\ensuremath{\simeq}1.4$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ dip recently observed at 50 GeV/c persists to higher incident momenta. Proton-proton measurements made at the same beam momenta show similar structure.

Gas Electron Multipliers (GEM) are an interesting technology under consideration for the future upgrade of the forward region of the CMS muon system, specifically in the $1.6<| \eta |<2.4$ endcap region. With a sufficiently fine segmentation GEMs can provide precision tracking as well as fast trigger information. The main objective is to contribute to the improvement of the CMS muon trigger. The construction of large-area GEM detectors is challenging both from the technological and production aspects. In view of the CMS upgrade we have designed and built the largest full-size Triple-GEM muon detector, which is able to meet the stringent requirements given the hostile environment at the high-luminosity LHC. Measurements were performed during several test beam campaigns at the CERN SPS in 2010 and 2011. The main issues under study are efficiency, spatial resolution and timing performance with different inter-electrode gap configurations and gas mixtures. In this paper results of the performance of the prototypes at the beam tests will be discussed.

The Compact Muon Solenoid (CMS) experiment at the LHC is planning an upgrade of its muon detection system aiming to extend the muon detection capabilities in the forward region with the installation of new muon stations based on Gas Electron Multiplier (GEM) and Resistive Plate Chambers (RPC) technologies during the so-called Phase-2 upgrade scenario. With the imminent increase on luminosity to 5 × 1034cm-2s-1 and center of mass collision energy of 14 TeV an unprecedented and hostile radiation environment will be created, the most affected detectors will be the ones located in the forward region where the intense flux of neutrons and photons could potentially degrade the detector performance. Using FLUKA simulation the expected radiation environment is estimated for the regions of interest, possible shielding scenarios are proposed and the effect on the detector performance is discussed.

The ultimate goal of this experiment is to record about 100 million bottom events tagged with a lepton trigger. It is only with a sample of this size that CP violation and very rare decays from bottom can be studied. In order to produce 109 bottom events an integrated luminosity of 500 pb-1 is needed, which could be accomplished in a one year run of 107 sec at a luminosity of 5 x 1031 cm-2sec-1, assuming a total bottom cross section of 10 μbarns. With a trigger efficiency of about 10 percent, the goal of about 108 bottom events recorded seems attainable. Having produced and recorded this large data set, the task of reconstructing these events and extracting physics will be a tremendous challenge to the detector design and physicists involved. This experiment begins the process of how t,o best tag a very large sample of bottom events in a high energy hadron collider environment. The most challenging aspects concern studying the secondary vertices when multiple scattering effects are large and detecting very soft leptons in a busy tracking environment. This will lead to a better exploitation of the high luminosity Tevatron as well as eventually preparing for the SSC.

We present analytical calculations, Finite Element Analysis modelling, and physical measurements of the interstrip capacitances for different potential strip geometries and dimensions of the readout boards for the GE2/1 triple-Gas Electron Multiplier detector in the CMS muon system upgrade. The main goal of the study is to find configurations that minimize the interstrip capacitances and consequently maximize the signal-to-noise ratio for the detector. We find agreement at the 1.5–4.8% level between the two methods of calculations and on the average at the 17% level between calculations and measurements. A configuration with halved strip lengths and doubled strip widths results in a measured 27–29% reduction over the original configuration while leaving the total number of strips unchanged. We have now adopted this design modification for all eight module types of the GE2/1 detector and will produce the final detector with this new strip design.

Single-sided and double-sided AC-coupled Si microstrip detectors read out with Berkeley SVX version D VLSI chips have been tested in a 227-GeV/c charged pion beam at Fermilab. Pulse height information, cluster size, and spatial resolution have been studied as functions of incident beam angle. It was found that the experimental spatial resolution agrees with Monte Carlo predictions and that the average pulse height and cluster size increase accordingly with increasing angle of particle incidence from the normal. The results of the beam tests are presented in detail.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Data are presented on elastic $\ensuremath{\pi}p$ and $\mathrm{Kp}$ scattering for values of $\ensuremath{-}t$ up to 2.5 and 3.5 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ at incident momenta of 100 and 200 GeV/c, respectively. All of the cross sections are found to be nearly identical, although there is some momentum dependence of the ${\ensuremath{\pi}}^{+}p$ data; a small systematic difference observed between pion and kaon data cannot be explained by geometrical scaling.

During the future LHC upgrade planned in 2018, the forward endcap region of the CMS muon spectrometer will be upgraded with GEM chambers. GEM technology is able to withstand the radiation environment expected in the forward region. The GE1/1 station will be included in the muon L1 trigger, allowing to keep low p(T) threshold even at high luminosity. Moreover, it will bring detection redundancy in the most critical part of the CMS muon system, along with benefits to muon reconstruction performance.

For the High-Luminosity LHC (HL-LHC) phase the CMS GEM Collaboration is planning to install new large-size (990×220–455mm2) triple-GEM detectors, equipped with a new readout system, in the forward region of the muon system (1.5< |η| <2.2) of the CMS detector. Combining triggering and tracking functionalities the new triple-foil Gas Electron Multiplier (GEM) chambers will improve both the performance of the CMS muon trigger and the muon reconstruction/identification in CMS experiment. The addition of triple-GEM chambers to the forward region of the CMS muon system will add a necessary layer of redundancy. Starting from 2009 the CMS GEM Collaboration has built several small and full-size prototypes with different geometries, keeping improving the assembly techniques. All these prototypes have been tested in laboratories as well as with beam tests at the CERN Super Proton Synchrotron (SPS) and at Fermi National Accelerator Laboratory. In this contribution we will report on the status of the CMS upgrade project with triple-GEM chambers and its impact on the CMS performance as well as the hardware architectures and expected capability of the CMS GEM readout system.

We describe recent progress in accelerator-based experiments in high-energy particle physics and progress in theoretical investigations in particle physics. We also describe future plans in these areas.

Gas Electron Multipliers (GEM) are an interesting technology under consideration for the future upgrade of the forward region of the CMS muon system, specifically in the $1.6

The tracking performance of a 0.64 cm square double-sided AC-coupled detector manufactured by Hamamatsu Photonics Inc. has been evaluated in a test beam of 227 GeV/c pions at Fermilab. The detector was fabricated with 50 μm pitch on the ohmic (n) side and 25 μm pitch on the diode (p) side. Readout pitch for both sides was 50 μm and was implemented with a Berkeley designed SVX-D IC/SRS/SDA sequencer system. Measurements were made of signal-to-noise, charge correlation characteristics and resolution vs. angle of incidence in the range from 0° to 60° with analog pulse height information. Measurements were made at room temperature, −12°C and −20°C.

We present a method to align between sections of a particle tracking detector exploiting the fact that most of the tracks in an event originate from a common spatial point. The method optimizes the reconstruction of interaction vertices of high energy particle collisions and is particularly useful for aligning sections of a detector which cover different ranges of the 4/spl pi/ solid angle. A fast algorithm, suitable for online use, is derived. We demonstrate this method for the P238 vertex detector and present results with data and simulation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A charge coupled device (CCD) electronic image sensor is used for a microscope television capable of detecting single grains in nuclear emulsion.

Three recent results on charm physics are presented based on Run II data using the Fermilab Tevatron Collider. The DØ collaboration reports preliminary results on the first observation of the rare decay Ds±→π±ϕ, ϕ→μ+μ−, a measurement of the branching fraction for D± to the same final state, and an upper limit for the non-resonant decay D±→π±μ+μ−. The CDF collaboration reports a preliminary measurement of the angular distribution for X(3872)→J/ψπ+π− and restricts the X(3872) quantum numbers to JPC=1++ or 2−+. Also, CDF reports a measurement of the ratio of branching fractions of the rare (doubly Cabibbo-suppressed) decay D0→K+π− and the Cabibbo-favored decay D0→K−π+ (and charge conjugate decays).

Single sided and double sided AC coupled silicon microstrip detectors read out with Berkeley SVX version D VSLI chips[4] have ban tested in a 227 GeV/c charged pion beam at Fermilab. Pulse height infomation, clusta size and spanal resolution have been studied as a function of incident beam angle. It was found that the experimental spaual resolution agrees well with montecarlo pmhcaons and that the average pulse height and cluster size increase accordingly with mcrcasmg angle of particle inctdence from the normal.

The requirements for a linear collider muon detector are discussed and a solution is presented based on solid scintillating strips with embedded wavelength shifting optical fibers. Multi-anode photo-multiplier tubes are a good candidate for photon detection. Their single photo-electron response can be calibrated using fast pulses from light-emitting diodes.

Preliminary results are reported for measurements of the masses and widths of the L = 1 charm mesons [Formula: see text] and [Formula: see text], using data from Run II of the Fermilab Tevatron. Final results are presented for CP asymmetry and relative branching fraction for the decays D 0 → K + K - and π + π - .

Abstract In 2018, a system of large-size triple-GEM demonstrator chambers was installed in the CMS experiment at CERN's Large Hadron Collider (LHC). The demonstrator's design mimicks that of the final detector, installed for Run-3. A successful Monte Carlo (MC) simulation of the collision-induced background hit rate in this system in proton-proton collisions at 13 TeV is presented. The MC predictions are compared to CMS measurements recorded at an instantaneous luminosity of 1.5 ×10 34 cm -2 s -1 . The simulation framework uses a combination of the FLUKA and GEANT4 packages. FLUKA simulates the radiation environment around the GE1/1 chambers. The particle flux by FLUKA covers energy spectra ranging from 10 -11 to 10 4 MeV for neutrons, 10 -3 to 10 4 MeV for γ's, 10 -2 to 10 4 MeV for e ± , and 10 -1 to 10 4 MeV for charged hadrons. GEANT4 provides an estimate of the detector response (sensitivity) based on an accurate description of the detector geometry, the material composition, and the interaction of particles with the detector layers. The detector hit rate, as obtained from the simulation using FLUKA and GEANT4, is estimated as a function of the perpendicular distance from the beam line and agrees with data within the assigned uncertainties in the range 13.7-14.5%. This simulation framework can be used to obtain a reliable estimate of the background rates expected at the High Luminosity LHC.

The decay J/ψ → μ + μ - is one of the main trigger channels in the HERA-B experiment. The muon deterctor and the trigger hardware are described. Results are reported from the initial trigger commissioning that includes the Muon Pretrigger and Second Level Trigger. A J/ψ mass peak with good signal to background ratio is obtained.

Single- and double-sided AC-coupled detectors and double-sided DC-coupled detectors read out with the Berkeley SVXD chip are being studied. The authors report on the signal and noise characteristics for typical single channels and the channel-to-channel variations in noise, gain, and pedestal values. Because collider detectors encounter tracks at all angles of incidence, the authors studied the response of the prototypes over a wide range of angles to see whether the cluster size and charge sharing properties of the various detectors are different. For angles at approximately 0 degrees , the resolution of the double-sided detector is 4.5 mu m on the ohmic side and 3.5 mu m for the single-sided AC coupled detector. The signal-to-noise ratio for the double-sided detector is 25:1, while for the single-sided detector it is 38:1.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Recent results on the hadroproduction of charm and beauty are discussed in the context of the current theoretical and experimental status. The areas covered include production of open charm and beauty particles and charm and beauty quarkonia. Experimental results from both fixed target and colliding beam experiments are presented and compared to theoretical predictions. Predictions based on QCD perturbation theory are generally successful in explaining the shapes of differential cross sections but underestimate the scale of the cross section by factors of 2-3. An exception is production of the vector meson quarkonia which cannot be satisfactorily explained by perturbative processes alone.

We present the first measurement of the atomic mass dependence of central \Xi^- and \overline{\Xi}^+ production. It is measured using a sample of 22,459 \Xi^-'s and \overline{\Xi}^+'s produced in collisions between a 250 GeV \pi^- beam and targets of beryllium, aluminum, copper, and tungsten. The relative cross sections are fit to the two parameter function \sigma_0 A^\alpha, where A is the atomic mass. We measure \alpha = 0.924+-0.020+-0.025, for Feynman-x in the range -0.09 < x_F < 0.15.

Recent results on the hadroproduction of charm and beauty are discussed in the context of the current theoretical and experimental status. The areas covered include production of open charm and beauty particles and charm and beauty quarkonia. Experimental results from both fixed target and colliding beam experiments are presented and compared to theoretical predictions. Predictions based on QCD perturbation theory are generally successful in explaining the shapes of differential cross sections but underestimate the scale of the cross section by factors of 2-3. An exception is production of the vector meson quarkonia which cannot be satisfactorily explained by perturbative processes alone.

An overview of a SSC R D program for silicon vertex detector development is presented. The current test program with silicon microstrip and pixel detectors is discussed and selected results of beam tests are presented including measurements of position resolution as a function of angle of incidence. Plans for future tests are also discussed. 10 refs., 4 figs.

Abstract

Silicon vertex detectors will be crucial to the success of high rate bottom physics experiments at hadron colliders. A geometrical layout and detector segmentation scheme is presented that is optimized for the production and decay properties of b-particles. While existing p-i-n diode sensors are adequate, new VLSI readout electronics must be developed that are faster and more radiation tolerant than existing devices. Technology is available from the telecommunications industry for streaming the data off the vertex detector. This information can be manipulated with wafer-scale integration processors for use in triggering.

Two AC-coupled silicon strip devices were operated in a Fermilab test beam with Berkeley SVXD readout. Operation of the detectors is described and results for the spatial resolution are given.

We report on the production of D± mesons using a 250 GeV/c π− beam incident on target of Be, Al, Cu and W. Over the range 0.0<xF<0.9 the data for dσ/dxF are well desribed by a function of the form (1−xF)n with n = 3.08±0.25. We find the difference between the values of n for D+ and D− to be less than 1.3 at 90% C.L. Also, there is no significant dependence of n on atomic number. We compare our preliminary results with those of other experiments and with predictions based on perturbative QCD.

We measure the differential cross section with respect to Feynman‐x (xF) and transverse momentum (PT) for charm meson production using targets of Be, Al, Cu and W. In the range 0.1≤xF≤0.7, dσ/dxF is well fit by the form (1−xF)n with n=3.9±0.2. The difference between n values for D− and D+ is 1.1±0.4. However, we find an asymmetry of 0.18±0.04 favoring the production of D− compared to D+. In the lower PT range, ≤2 GeV, dσ/dP2T is well fit by the form exp(−b×P2T) with b=1.03±0.04 GeV−2, while in the higher PT range, 0.8 to 3.6 GeV, it is well fit by the form exp(−b’×PT) with b’=2.76±0.06 GeV−1. The shape of the differential cross section has no significant dependence on atomic mass of the target material.

We have measured a signal‐to‐noise of 37:1 at room temperature for 227 GeV pions at Fermilab on the n(ohmic)‐side of a Hamamatsu AC‐coupled double‐sided silicon microstrip detector with 0.64 cm long strips. Position resolutions at normal incidence of 3.5±0.4 μm (10.4±0.5 μm) were obtained for the p‐side (n‐side) which had 25 μm (50 μm) pitch and 50 μm readout. The effects of radiation damage on the n‐side have also been measured with a 60Co source. Phase‐gain measurements imply that the accumulation layer bias capacitance and AC‐coupling capacitance are constant with dose up to 5 Mrad with values of 1.2 pf and 12 pf per strip respectively. The bias resistance per strip has a value of ∼0.8 MΩ at 0 and 5 Mrad and ∼0.4 MΩ at doses of 20–100 Krad.