Search

Single neutron- and proton-removal cross sections have been systematically measured for 72 medium-mass neutron-rich nuclei around Z=50 and energies around 900A MeV using the FRagment Separator (FRS) at GSI. Neutron-removal cross sections are described by considering the knock-out process together with initial- and final-state interactions. Proton-removal cross sections are, however, significantly smaller than predicted by the same calculations. The observed difference can be explained as due to the knockout of short-correlated protons in neutron-proton dominating pairs.

A prototype of a luminometer, designed for a future e+e- collider detector, and consisting at present of a four-plane module, was tested in the CERN PS accelerator T9 beam. The objective of this beam test was to demonstrate a multi-plane tungsten/silicon operation, to study the development of the electromagnetic shower and to compare it with MC simulations. The Moli\`ere radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using a parametrization of the shower shape. Very good agreement was found between data and a detailed Geant4 simulation., Comment: Paper published in Eur. Phys. J., includes 25 figures and 3 Tables

The Compact Linear Collider (CLIC) is a multi-TeV high-luminosity linear e+e- collider under development. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in a staged approach with three centre-of-mass energy stages ranging from a few hundred GeV up to 3 TeV. The first stage will focus on precision Standard Model physics, in particular Higgs and top-quark measurements. Subsequent stages will focus on measurements of rare Higgs processes, as well as searches for new physics processes and precision measurements of new states, e.g. states previously discovered at LHC or at CLIC itself. In the 2012 CLIC Conceptual Design Report, a fully optimised 3 TeV collider was presented, while the proposed lower energy stages were not studied to the same level of detail. This report presents an updated baseline staging scenario for CLIC. The scenario is the result of a comprehensive study addressing the performance, cost and power of the CLIC accelerator complex as a function of centre-of-mass energy and it targets optimal physics output based on the current physics landscape. The optimised staging scenario foresees three main centre-of-mass energy stages at 380 GeV, 1.5 TeV and 3 TeV for a full CLIC programme spanning 22 years. For the first stage, an alternative to the CLIC drive beam scheme is presented in which the main linac power is produced using X-band klystrons., Comment: 57 pages, 27 figures, 12 tables, published as CERN Yellow Report. Updated version: Minor layout changes for print version

The Compact Linear Collider (CLIC) is an option for a future e+e- collider operating at centre-of-mass energies up to 3 TeV, providing sensitivity to a wide range of new physics phenomena and precision physics measurements at the energy frontier. This paper is the first comprehensive presentation of the Higgs physics reach of CLIC operating at three energy stages: sqrt(s) = 350 GeV, 1.4 TeV and 3 TeV. The initial stage of operation allows the study of Higgs boson production in Higgsstrahlung (e+e- -> ZH) and WW-fusion (e+e- -> Hnunu), resulting in precise measurements of the production cross sections, the Higgs total decay width Gamma_H, and model-independent determinations of the Higgs couplings. Operation at sqrt(s) > 1 TeV provides high-statistics samples of Higgs bosons produced through WW-fusion, enabling tight constraints on the Higgs boson couplings. Studies of the rarer processes e+e- -> ttH and e+e- -> HHnunu allow measurements of the top Yukawa coupling and the Higgs boson self-coupling. This paper presents detailed studies of the precision achievable with Higgs measurements at CLIC and describes the interpretation of these measurements in a global fit., Comment: 42 pages, 29 figures, accepted for publication in the European Physical Journal C

A prototype of a luminometer, designed for a future e+e- collider detector, was tested in the CERN PS accelerator T9 testbeam. The objective of this test beam was to demonstrate a multi-plane operation, to study the development of the electromagnetic shower and to compare it with MC simulations., Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 Novem- ber 2015. 15 pages and 18 figures

The future Compact Linear Collider (CLIC) offers a possibility for a rich precision physics programme, in particular in the Higgs sector through the energy staging. This is the first paper addressing the measurement of the Standard Model Higgs boson decay into two muons at 1.4 TeV CLIC. With respect to similar studies at future linear colliders, this paper includes several novel contributions to the statistical uncertainty of the measurement. The later includes the Equivalent Photon Approximation and realistic forward electron tagging based on energy deposition maps in the forward calorimeters, as well as several processes with the Beamstrahlung photons that results in irreducible contribution to the signal. In addition, coincidence of the Bhabha scattering with the signal and background processes is considered, altering the signal selection efficiency. The study is performed using a fully simulated CLIC_ILD detector model. It is shown that the branching ratio for the Higgs decay into a pair of muons BR(${H\rightarrow\mu^+\mu^-}$) times the Higgs production cross-section in $WW$-fusion $\sigma(H\nu\bar{\nu})$ can be measured with 38% statistical accuracy at ${\sqrt{s} =\text{1.4 TeV}}$, assuming an integrated luminosity of 1.5 ab$^{-1}$ with unpolarised beams. If 80% electron beam polarisation is considered, the statistical uncertainty of the measurement is reduced to 25%. Systematic uncertainties are negligible in comparison to the statistical uncertainty., Comment: arXiv admin note: substantial text overlap with arXiv:1412.5791

The potential for the measurement of the branching ratio of the Standard Model-like Higgs boson decay into a mu+mu- pair at 1.4 TeV CLIC is analysed. The study is performed using the fully simulated CLIC_ILD detector concept, taking into consideration all the relevant physics and the beam-induced backgrounds. Despite the very low branching ratio of the H->mu+mu- decay, we show that the product of the branching ratio times the Higgs production cross section can be measured with a statistical uncertainty of 38 percent, assuming an integrated luminosity of 1.5 ab^-1 collected in five years of the detector operation at the 1.4 TeV CLIC with unpolarised beams. With polarised beams (-80%, +30%), the statistical uncertainty is better than 25%., Comment: 17 pages, 13 figures

Background:The design of new nuclear reactors and transmutation devices requires to reduce the present neutron cross section uncertainties of minor actinides. Purpose: Reduce the $^{243}$Am(n,$\gamma$) cross section uncertainty. Method: The $^{243}$Am(n,$\gamma$) cross section has been measured at the n_TOF facility at CERN with a BaF$_{2}$ Total Absorption Calorimeter, in the energy range between 0.7 eV and 2.5 keV. Results: The $^{243}$Am(n,$\gamma$) cross section has been successfully measured in the mentioned energy range. The resolved resonance region has been extended from 250 eV up to 400 eV. In the unresolved resonance region our results are compatible with one of the two incompatible capture data sets available below 2.5 keV. The data available in EXFOR and in the literature has been used to perform a simple analysis above 2.5 keV. Conclusions: The results of this measurement contribute to reduce the $^{243}$Am(n,$\gamma$) cross section uncertainty and suggest that this cross section is underestimated up to 25% in the neutron energy range between 50 eV and a few keV in the present evaluated data libraries.

Two special calorimeters are foreseen for the instrumentation of the very forward region of an ILC or CLIC detector; a luminometer (LumiCal) designed to measure the rate of low angle Bhabha scattering events with a precision better than 10$^{-3}$ at the ILC and 10$^{-2}$ at CLIC, and a low polar-angle calorimeter (BeamCal). The latter will be hit by a large amount of beamstrahlung remnants. The intensity and the spatial shape of these depositions will provide a fast luminosity estimate, as well as determination of beam parameters. The sensors of this calorimeter must be radiation-hard. Both devices will improve the e.m. hermeticity of the detector in the search for new particles. Finely segmented and very compact electromagnetic calorimeters will match these requirements. Due to the high occupancy, fast front-end electronics will be needed. Monte Carlo studies were performed to investigate the impact of beam-beam interactions and physics background processes on the luminosity measurement, and of beamstrahlung on the performance of BeamCal, as well as to optimise the design of both calorimeters. Dedicated sensors, front-end and ADC ASICs have been designed for the ILC and prototypes are available. Prototypes of sensor planes fully assembled with readout electronics have been studied in electron beams., Comment: 61 pages, 51 figures

Detector-plane prototypes of the very forward calorimetry of a future detector at an e+e- collider have been built and their performance was measured in an electron beam. The detector plane comprises silicon or GaAs pad sensors, dedicated front-end and ADC ASICs, and an FPGA for data concentration. Measurements of the signal-to-noise ratio and the response as a function of the position of the sensor are presented. A deconvolution method is successfully applied, and a comparison of the measured shower shape as a function of the absorber depth with a Monte-Carlo simulation is given., Comment: 25 pages, 32 figures, revised version following comments from referees

In these proceedings a novel approach to deal with the beam-induced effects in luminosity measurement is presented. Based on the relativistic kinematics of the collision frame of the Bhabha process, the beam-beam related uncertainties can be reduced to the permille level independently of a precision with which the beam parameters are known. Specific event selection combined with the corrective methods we introduce, leads to the systematic uncertainty from the beam-induced effects to be at a few permille level in the peak region above the 80% of the nominal centre-of-mass energies at ILC., Comment: Talk presented on behalf of the FCAL Collaboration at the International Workshop on Future Linear Colliders (LCWS13) Tokyo, Japan, 11-15 November 2013

The branching fraction measurement of the SM-like Higgs boson decay into two muons at 1.4 TeV CLIC will be described in this paper contributed to the LCWS13. The study is performed in the fully simulated ILD detector concept for CLIC, taking into consideration all the relevant physics and the beam-induced backgrounds, as well as the instrumentation of the very forward region to tag the high-energy electrons. Higgs couplings are known to be sensitive to BSM physics and we prove that BR times the Higgs production cross section can be measured with approximately 35.5% statistical accuracy in four years of the CLIC operation at 1.4 TeV centre-of-mass energy with unpolarised beams. The result is preliminary as the equivalent photon approximation is not considered in the cross-section calculations. This study complements the Higgs physics program foreseen at CLIC., Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS13), Tokyo, Japan, 11-15 November 2013 on behalf of the CLIC Detector and Physics Collaboration

In this paper we describe a method of luminosity measurement at the future linear collider ILC that estimates and corrects for the impact of the dominant sources of systematic uncertainty originating from the beam-induced effects and the background from physics processes. Based on the relativistic kinematics of the collision frame of the Bhabha process, the beam-beam related uncertainty is reduced to a permille independently of the precision with which the beam parameters are known. With the specific event selection, different from the isolation cuts based on topology of the signal used at LEP, combined with the corrective methods we introduce, the overall systematic uncertainty in the peak region above 80% of the nominal center-of-mass energy meets the physics requirements to be at the few permille level at all ILC energies., Comment: Accepted for publication in JINST (submission JINST_016P_0413)

Total cross sections for proton- and deuteron-induced-fission of 208Pb and 238U have been determined in the energy range between 500 MeV and 1 GeV. The experiment has been performed in inverse kinematics at GSI Darmstadt, facilitating the counting of the projectiles and the identification of the reaction products. High precision between 5 and 7 percent has been achieved by individually counting the beam particles and by registering both fission fragments in coincidence with high efficiency and full Z resolution. Fission was clearly distinguished from other reaction channels. The results were found to deviate by up to 30 percent from Prokofiev's systematics on total fission cross sections. There is good agreement with an elaborate experiment performed in direct kinematics., Comment: 18 pages, 12 figures

The gas-flow reduction factor of the second forward Differential Pumping Section (DPS2-F) for the KATRIN experiment was determined using a dedicated vacuum-measurement setup and by detailed molecular-flow simulation of the DPS2-F beam tube and of the measurement apparatus. In the measurement, non-radioactive test gases deuterium, helium, neon, argon and krypton were used, the input gas flow was provided by a commercial mass-flow controller, and the output flow was measured using a residual gas analyzer, in order to distinguish it from the outgassing background. The measured reduction factor with the empty beam tube at room temperature for gases with mass 4 is 1.8(4)E4, which is in excellent agreement with the simulated value of 1.6E4. The simulated reduction factor for tritium, based on the interpolated value for the capture factor at the turbo-molecular pump inlet flange is 2.5E4. The difference with respect to the design value of 1E5 is due to the modifications in the beam tube geometry since the initial design, and can be partly recovered by reduction of the effective beam tube diameter., Comment: 10 figures, 10 pages, version accepted for publication the Vacuum journal

Production cross-sections and longitudinal velocity distributions of the projectile-like residues produced in the reactions 112Sn + 112Sn and 124Sn + 124Sn both at an incident beam energy of 1 AGeV were measured with the high-resolution magnetic spectrometer, the Fragment Separator (FRS) of GSI. For both reactions the characteristics of the velocity distributions and nuclide production cross sections were determined for residues with atomic number Z $\geq$ 10. A comparison of the results of the two reactions is presented., Comment: 14 pages, 12 figures

The fragmentation of neutron-rich 132Sn nuclei produced in the fission of 238U projectiles at 950 MeV/u has been investigated at the FRagment Separator (FRS) at GSI. This work represents the first investigation of fragmentation of medium-mass radioactive projectiles with a large neutron excess. The measured production cross sections of the residual nuclei are relevant for the possible use of a two-stage reaction scheme (fission+fragmentation) for the production of extremely neutron-rich medium-mass nuclei in future rare-ion-beam facilities. Moreover, the new data will provide a better understanding of the "memory" effect in fragmentation reactions., Comment: 5 pages, 3 figures

An electron-impact ion source based on photoelectron emission was developed for ionization of gases at pressures below 1e-4 mbar in an axial magnetic field in the order of 5 T. The ion source applies only DC fields, which makes it suitable for use in the presence of equipment sensitive to radio-frequency (RF) fields. The ion source was succesfully tested under varying conditions regarding pressure, magnetic field and magnetic-field gradient, and the results were studied with the help of simulations. The processes in the ion source are well understood and possibilities for further optimization of generated ion currents are clarified., Comment: 10 pages, 13 figures

The KArlsruhe TRItium Neutrino experiment KATRIN aims at improving the upper limit of the mass of the electron antineutrino to about 0.2 eV (90% c.l.) by investigating the beta-decay of tritium gas molecules. The experiment is currently under construction to start first data taking in 2012. One source of systematic uncertainties in the KATRIN experiment is the formation of ion clusters when tritium decays and decay products interact with residual tritium molecules. It is essential to monitor the abundances of these clusters since they have different final state energies than tritium ions. For this purpose, a prototype of a cylindrical Penning trap has been constructed and tested at the Max-Planck-Institute for Nuclear Physics in Heidelberg, which will be installed in the KATRIN beam line. This system employs the technique of Fourier-Transform Ion-Cyclotron-Resonance in order to measure the abundances of the different stored ion species., Comment: 7 pages, 6 figures

Recently, a series of dedicated inverse-kinematics experiments performed at GSI, Darmstadt, has brought an important progress in our understanding of proton and heavy-ion induced reactions at relativistic energies. The nuclear reaction code ABRABLA that has been developed and benchmarked against the results of these experiments has been used to calculate nuclide production cross sections at different energies and with different targets and beams. These calculations are used to estimate nuclide production rates by protons in thick targets, taking into account the energy loss and the attenuation of the proton beam in the target, as well as the low-energy fission induced by the secondary neutrons. The results are compared to the yields of isotopes of various elements obtained from different targets at CERN-ISOLDE with 600 MeV protons, and the overall extraction efficiencies are deduced. The dependence of these extraction efficiencies on the nuclide half-life is found to follow a simple pattern in many different cases. A simple function is proposed to parameterize this behavior in a way that quantifies the essential properties of the extraction efficiency for the element and the target - ion-source system in question., Comment: 46 pages, 49 figures, background information on http://www-w2k.gsi.de/charms/