R. W. Assmann

Publication List Details

Period

1992 - 2009

Number

179

Co-Authors

Measurements of heavy ion beam losses from collimation (2009)

Bruce, R., Assmann, R. W., Bellodi, G., Bracco, C., Braun, H. H., Gilardoni, S., ...

The collimation efficiency for Pb ion beams in the LHC is predicted to be lower than requirements. Nuclear fragmentation and electromagnetic dissociation in the primary collimators create fragments...

Streak-Camera Measurements of the PEP-II (2007)

High-energy Ring, A. S. Fisher, R. W. Assmann, A. H. Lumpkin, B. Zotter, J. Byrd, ...

Abstract. The third commissioning run of the PEP-II High-Energy Ring (HER, the 9 GeV electron ring), in January 1998, included extensive measurements of single-bunch and multibunch fills using...

Scenarios for Beam Commissioning of the LHC collimation system (2007)

Bracco, C, Assmann, R W, Redaelli, S, Robert-Demolaize, R

A system of collimators has been designed to protect the superconducting LHC magnets against quench and damage from the high intensity proton beams. The considerable number of collimators and the...

The final collimation system for the LHC (2006)

Assmann, R W, Aberle, O, Bellodi, G, Bertarelli, A, Bracco, C, Braun, H, ...

The LHC collimation system has been re-designed over in order to address the unprecedented challenges that are faced with the 360 MJ beams at 7 TeV. The layout of the LHC has now been frozen and a...

An Improved Cllimation System for the LHC (2004)

Assmann, R W, Aberle, O, Bertarelli, A, Braun, H, Brugger, M, Brüning, Oliver Simon, ...

The handling of the high-intensity LHC beams in a super-conducting environment requires a high-robustness collimation system with unprecedented cleaning efficiency. For gap closures down to 2.2 mm no...

Calibration of centre-of-mass energies at LEP 2 for a precise measurement of the W boson mass (2004)

Assmann, R W, Barbero-Soto, E, Cornuet, D, Dehning, Bernd, Hildreth, M, Matheson, J, ...

The determination of the centre-of-mass energies for all LEP 2 running is presented. Accurate knowledge of these energies is of primary importance to set the absolute energy scale for the measurement...

Review of ultra high-gradient acceleration schemes, results of experiments (2004)

Assmann, R W

A dramatic improvement in energy gain per unit cost is mandatory for the future of very high energy accelerators, for which RF- acceleration would be replaced by new techniques. Several schemes have...

Emittance optimization with dispersion free steering at LEP (2004)

Assmann, R W, Raimondi, Pantaleo, Roy, G, Wenninger, J

Residual vertical dispersion can be a significant performance limitation for the LEP collider because the associated vertical emittance increase reduces the luminosity of the machine. To make the...

Designing and Building a Collimation System for the High-Intensity LHC Beam (2003)

Assmann, R W, Aberle, O, Baishev, I S, Bruno, L, Brugger, M, Chiaveri, Enrico, ...

The Large Hadron Collider (LHC) will collide proton beams at 14 TeV c.m. with unprecedented stored intensities. The transverse energy density in the beam will be about three orders of magnitude...

Tools for Predicting Cleaning Efficiency in the LHC (2003)

Assmann, R W, Baishev, I S, Brugger, M, Hayes, M, Jeanneret, J B, Kain, V, ...

The computer codes SIXTRACK and DIMAD have been upgraded to include realistic models of proton scattering in collimator jaws, mechanical aperture restrictions, and time-dependent fields. These new...

Status of the CLIC study on magnet stabilisation and time-dependent luminosity (2002)

Assmann, R W, Coosemans, Williame, Guignard, Gilbert, Leros, Nicolas, Redaelli, S, Schnell, Wolfgang, ...

The nanometer beam size at the CLIC interaction point imposes magnet vibration tolerances that range from 0.2 nm to a few nanometers. This is well below the floor vibra-tion usually observed. A test...

CLIC simulations from the start of the linac to the interaction point (2002)

Schulte, Daniel, Assmann, R W, Blair, G A, D'Amico, T E, Leros, Nicolas, Redaelli, S, ...

Simulations for linear colliders are traditionally performed separately for the different sub-systems, like damping ring, bunch compressor, linac, and beam delivery. The beam properties are usually...

Requirements for the LHC collimation system (2002)

Assmann, R W, Baishev, I S, Brugger, M, Bruno, L, Burkhardt, H, Burtin, G, ...

The LHC requires efficient collimation during all phases of the beam cycle. Collimation plays important roles in prevention of magnet quenches from regular beam diffusion, detection of abnormal beam...

Review of ultra high-gradient acceleration schemes, results of experiments (2002)

Assmann, R W

A dramatic improvement in energy gain per unit cost is mandatory for the future of very high energy accelerators, for which RF-acceleration would be replaced by new tech-niques. Several schemes have...

The effect of cooling water on magnet vibrations (2002)

Redaelli, S, Assmann, R W, Coosemans, Williame, Schnell, Wolfgang

The quadrupole magnets in the CLIC Test Facility II (CTF2) incorporate a water cooling circuit. In the frame-work of the CLIC stability study, the mechanical vibrations of the magnets were measured...

Comparison of different tracking codes for beam delivery systems of linear colliders (2002)

Redaelli, S, Assmann, R W, Blair, G A, Burkhardt, H, Nosochkov, Yu M, Raubenheimer, T O, ...

The vertical RMS spot sizes at the interaction point of linear colliders are in the 1 nm to 5 nm range at beam en-ergies from 0.25 TeV to 1.5 TeV. Numerical tracking of particles through the magnetic...

Design Status of the CLIC Beam Delivery System (2002)

Aleksa, Martin, Assmann, R W, Blair, G A, Burkhardt, H, Faus-Golfe, A, Redaelli, S, ...

Recent developments on the CLIC collimation and final focus are described. The combination of a shortened linear, or alternative nonlinear, collimation section and a compact final focus substantially...

A Brief History of the LEP Collider (2002)

Assmann, R W, Lamont, M, Myers, S

The Large Electron Positron collider LEP at CERN was commissioned in 1989 and finished operation in November 2000. During this period it was operated in different modes, with different optics, at...

Polarization Issues at CLIC (2001)

Assmann, R W, Zimmermann, Frank

We review polarization issues for CLIC at 3 TeV centre-of-mass energy. An electron beam with about 80% polarization can be produced by an SLC-type photo-injector. Compton scattering off a high-power...

The CLIC Study of Magnet Stability and Time-dependent Luminosity Performance (2001)

Aleksa, Martin, Assmann, R W, Coosemans, Williame, Guignard, Gilbert, Leros, Nicolas, Mayoud, Michel, ...

The present parameters of the CLIC study require the collision of small emittance beams with a vertical spot size of 1 nm. The tolerances on vertical quadrupole vi-bration (above a few Hz) are as...

Overview of the CLIC Collimation design (2001)

Assmann, R W, Burkhardt, H, Fartoukh, Stéphane David, Jeanneret, J B, Pancin, J, Redaelli, S, ...

The collimation system of the Compact Linear Collider (CLIC) should simultaneously fulfill three different functions. It must (1) provide adequate halo collimation to render the detector background...

CLIC: a Two-Beam Multi-TeV $e\pm$ Linear Collider (2000)

Delahaye, J P, Wilson, Ian H, Assmann, R W, Becker, F, Bossart, Rudolf, Braun, H, ...

The CLIC study of a high-energy (0.5 - 5 TeV), high-luminosity (1034 - 1035 cm-2 sec-1) e± linear collider is presented. Beam acceleration using high frequency (30 GHz) normal-conducting structures...

Stability Considerations for Final Focus Systems of Future Linear Colliders (2000)

Assmann, R W, Jeanneret, J B, Verdier, A, Vos, L, Wildner, E, Zimmermann, Frank, ...

The final focus systems for the future linear colliders need to focus beams to nm-range spot sizes at the collision point. The design spot size varies from several nm for 500 GeV to the one nm range...

LEP Operation and Performance with 100 GeV Colliding Beams (2000)

Assmann, R W, Arduini, Gianluigi, Bailey, R, Butterworth, A, Collier, Paul, Cornelis, Karel, ...

Luminosity production in LEP was extended to 101 GeV beam energy in 1999 and 104.4 GeV in 2000. The performance was continually optimised, resulting in 1999 peak and integrated luminosities higher...

Luminosity and Beam Measurements used for Performance Optimisation in the LEP Collider (2000)

Assmann, R W, Berrig, O E, Burns, A, Dehning, Bernd, Ferrari, A, Jakob, H, ...

The vertical beam-beam parameter in LEP reached 0.083 in 1999. In order to achieve and maintain this high performance a number of different observables are continuously monitored and optimised. The...

A Method for Simultaneous Optimisation of Orbit and Dispersion in Storage Rings (2000)

Assmann, R W, Raimondi, Pantaleo, Roy, G, Wenninger, J

An algorithm for the simultaneous optimisation of orbit and dispersion in a storage ring is presented. Based on orbit and dispersion measurements the algorithm determines the optimal corrector...

Use of Movable Beam Position Monitors for Beam Size Measurements (2000)

Assmann, R W, Dehning, Bernd, Matheson, J

The use of beam position monitors (BPMs) as non-intercepting emittance monitors has been proposed in 1983 by Miller et al. The emittance measurement relies on the beam size dependency of the BPM...

The Beam-Beam Interaction in the Presence of Strong Radiation Damping (2000)

Assmann, R W, Cornelis, Karel

The beam-beam interaction in electron-positron storage rings depends strongly on the radiation damping. It has been shown before that the achievable beam-beam tune shift (the beam-beam limit) is a...

Nonlinearities in the Response of Beam Position Monitors (2000)

Assmann, R W, Dehning, Bernd, Matheson, B, Prochnow, J

At the LEP e+/e- collider at CERN, Geneva, a Spectrometer is used to determine the beam energy with a relative accuracy of 10-4. The Spectrometer measures the change in bending angle in a dipole...

Final-Focus System for CLIC at 3 TeV (2000)

Zimmermann, Frank, Assmann, R W, Guignard, Gilbert, Schulte, Daniel, Napoly, O

We describe a base-line optics for a 3-TeV final-focus system of the Compact Linear Collider (CLIC). The proposed system consists of an initial beta-matching region, two chromatic correction...

Design Status of the CLIC 3-TeV Beam Delivery System and Damping Rings (2000)

Assmann, R W, Burkhardt, H, Fartoukh, Stéphane David, Jeanneret, J B, Jowett, John M, Ruggiero, F, ...

We describe the present design status of beam delivery and damping rings for CLIC at 3 TeV cm energy, and outline our future plans. The beam delivery system comprises collimation, final focus and...

Status of the LEP2 Spectrometer Project (2000)

Dehning, Bernd, Assmann, R W, Bovet, Claude, Coosemans, Williame, Cornuet, D, Hidalgo, A, ...

The LEP spectrometer has been conceived to provide a determination of the beam energy with a relative accuracy of 10-4 in the LEP2 physics region where insufficient polarisation levels prevent the...

Nonlinear Response of Orbit Monitors (2000)

Assmann, R W, Dehning, Bernd, Matheson, J, Prochnow, J

The LEP Spectrometer is used to determine beam energy by measuring the bending angle of the beam in a dipole magnet, using six beam position monitors (BPMs), which must have an accuracy close to 10-6...

Physics and technology of the Next Linear Collider (2000)

Kuhlman, S, Adolphsen, C E, Aiello, R, Akemoto, M, Alley, R, Assmann, R W, ...

We present the current expectations for the design and physics program of an e+e- linear collider of center of mass energy 500 GeV -- 1 TeV. We review the experiments that would be carried out at...

Overview of LEP operation in 1998 (1999)

Arduini, Gianluigi, Assmann, R W, Bailey, R, Burkhardt, H, Butterworth, A, Collier, Paul, ...

After the installation of 32 additional RF cavities in the 1997-1998 shutdown LEP was operated at a beam energy of 94.5 GeV. The total integrated luminosity for the year 1998 clearly surpassed its...

Calibration of centre-of-mass energies at LEP1 for precise measurements of Z properties (1998)

Assmann, R W, Böge, M, Billen, R, Blondel, A, Bravin, Enrico, Bright-Thomas, P G, ...

The determination of the centre-of-mass energies from the LEP1 data for 1993, 1994 and 1995 is presented. Accurate knowledge of these energies is crucial in the measurement of the Z resonance param...

Search for charginos and neutralinos with R-parity violation at $\sqrt{s}$ = 130 and 136 GeV (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

Searches for charginos and neutralinos produced in e+e- collisions at centre-of-mass energies of 130 and 136 GeV have been performed under the assumptions that R-parity is not conserved, that the...

Strange b baryon production and lifetime in Z decays (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

In a data sample of approximately four million hadronic Z decays recorded with the ALEPH detector from 1990 to 1995, a search for the strange b baryon Xi_b is performed with a study of Xi-lepton...

Search for heavy lepton pair production in e+e- collisions at centre-of-mass energies of 130 and 136 GeV (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

A search for pair production of new heavy leptons has been performed assuming different scenarios for the mixing of the new particles with Standard Model leptons. No candidate events were found in a...

Mass Limit for the standard model Higgs boson with the full LEP I ALEPH data sample (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

background from the electroweak process e+e- --> l+ l- q qbar. This search results in a 95% C.L. lower limit on the Higgs boson mass of $63.9$~\Gcs. The reaction e+e- --> HZ* is used to search for...

Search for CP violation in the decay Z --> b$\overline{b}$g (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

About three million hadronic decays of the Z collected by ALEPH in the years 1991 to 1994 are used to search for anomalous CP violation beyond the Standard Model in the decay Z -> bbg. The study is...

Measurement of the b forward-backward asymmetry and mixing using high-p$_{\perp}$ leptons (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

The B0-B0# average mixing parameter chi and b forward-backward asymmetry are measured from a sample of 4,200,000 Z -> q qbar events recorded with the ALEPH detector at LEP in the years 1990-1995....

A study of single and multi-photon production in e+e- collisions at centre-of-mass energies of 130 and 136 GeV (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

The production of final states involving one or more energetic photons from e+e- collisions at high energies is studied using data collected by the ALEPH detector at LEP. The data consist of two...

Four-jet final state production in e+e- collisions at centre-of-mass energies of 130 and 136 GeV (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

The four-jet final state is analyzed to search for hadronic decays of pair-produced heavy particles. The analysis uses the ALEPH data collected at LEP in November 1995 at centre-of-mass energies of...

Studies of QCD in $e^{+}e^{-}\to$ hadrons at E$_{cm}$ = 130 and 136 GeV (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

Studies of QCD in $\mbox{e}^+\mbox{e}^- \rightarrow$ Hadrons at $E_{cm} = $} 130 and 136 GeV The ALEPH Collaboration An analysis of the properties of hadronic final states produced in...

Measurement of hadron and lepton-pair production from e+e- annihilation at centre-of-mass energies of 130 and 136 GeV (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

Hadronic and leptonic cross-sections and forward-backward asymmetries are measured using 5.7~pb$^{-1}$ of data taken with the ALEPH detector at LEP at $\cms$ energies of 130 and 136~GeV. The results...

Study of the B$_{s}^{0}\overline{B}_{s}^{0}$ oscillation frequency using D$_{s}^{-}$l$^{+}$ combinations in Z decays (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

A lower limit on the oscillation frequency of the BsBsbar system is obtained from approximately four million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1995. Leptons...

Measurement of the mass of the $\Lambda_{b}$ baryon (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

In a data sample of four million hadronic \Z\ decays collected with the ALEPH detector at LEP, four $\Lambda_b$ baryon candidates are exclusively reconstructed in the $\Lambda_b \rightarrow...

Determination of sin$^{2}\vartheta^{eff}_{W}$ using jet charge measurements in hadronic Z decays (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and backward hemisphere charges in hadronic decays of the Z. A data sample of...

Improved measurement of the $\overline{B}^{0}$ and B$^{-}$ meson lifetimes (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

The lifetimes of the \b0 \ and \bp\ mesons have been measured with the \aleph\ detector at LEP, using approximately 3 million hadronic Z decays collected in the period 1991--1994. In the first of...

Search for supersymmetric particles in e+e- collisions at centre-of-mass energies of 130 and 136 GeV (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

Search for supersymmetric particles in e+e- collisions at centre-of-mass energies of 130 and 136 GeV. Searches for supersymmetric particles produced in e+e- collisions at centre-of-mass energies of...

Measurement of $\Lambda$ polarization from Z decays (1996)

Buskulic, Damir, De Bonis, I, Décamp, D, Ghez, P, Goy, C, Lees, J P, ...

The polarization of \Lambda baryons from Z decays is studied with the {\sc Aleph} apparatus. Evidence of longitudinal polarization of s quarks from Z decay is observed for the first time. The...

Quark and gluon jet properties in symmetric three-jet events (1996)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

Quark and gluon jets with the same energy, 24GeV, are compared in symmetric three-jet configurations from hadronic Z decays observed by the ALEPH detector. Jets are defined using the Durham...

Measurement of $\Lambda_{b}$ polarization in Z decays (1995)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

The \Lambda_{\mathrm{b}} polarization in hadronic \mathrm{Z} decays is measured in semileptonic decays from the average energies of the charged lepton and the neutrino. In a data sample of...

Tau hadronic branching ratios (1995)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

From 64492 selected \tau-pair events, produced at the Z^0 resonance, the measurement of the tau decays into hadrons from a global analysis using 1991, 1992 and 1993 ALEPH data is presented. Special...

Measurement of the B$^{0}_{s}$ lifetime and production rate with D$^{-}_{s}$ l$^{+}$ combinations in Z decays (1995)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

The lifetime of the \bs meson is measured in approximately 3 million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1994. Seven different \ds decay modes were...

Measurement of the $\tau$ lepton lifetime (1995)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

The mean lifetime of the \tau lepton is measured in a sample of 25700 \tau pairs collected in 1992 with the ALEPH detector at LEP. A new analysis of the 1-1 topology events is introduced. In this...

Tau leptonic branching ratios (1995)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

A sample of 62249 \tau-pair events is selected from data taken with the ALEPH detector in 1991, 1992 and 1993. The measurement of the branching fractions for \tau decays into electrons and muons is...

A precise measurement of the average b hadron lifetime (1995)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

An improved measurement of the average b hadron lifetime is performed using a sample of 1.5 million hadronic Z decays, collected during the 1991-1993 runs of ALEPH, with the silicon vertex detector...

Production of excited beauty states in Z decays (1995)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

A data sample of about 3.0 million hadronic Z decays collected by the ALEPH experiment at LEP in the years 1991 through 1994, is used to make an inclusive selection of B~hadron events. In this event...

Limit on B$^{0}_{s}$ oscillation using a jet charge method (1995)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

A lower limit is set on the B_{s}^{0} meson oscillation parameter \Delta m_{s} using data collected from 1991 to 1994 by the ALEPH detector. Events with a high transverse momentum lepton and a...

Measurements of the charged particle multiplicity distribution in restricted rapidity intervals (1995)

Buskulic, Damir, Casper, David William, De Bonis, I, Décamp, D, Ghez, P, Goy, C, ...

Charged particle multiplicity distributions have been measured with the ALEPH detector in restricted rapidity intervals |Y| \leq 0.5,1.0, 1.5,2.0\/ along the thrust axis and also without restriction...

Lepton beam polarization at LEP (1995)

Assmann, R W, Blondel, A, Dehning, Bernd, Drees, A, Grosse-Wiesmann, P, Grote, H, ...

Results from studies on transverse polarization in LEP over the past two years are presented. A single beam transverse polarization level of 57% at 45 GeV was reached adopting strategies to...