Searcharxiv⌕ Search

arXiv subjects

Matthias Schott

Publications and source records attributed to Matthias Schott.

72 records · Page 4Linked to original sources

Opportunities and Challenges of Standard Model Production Cross Section Measurements at 8 TeV using CMS Open Data

The CMS Open Data project offers new opportunities to measure cross sections of standard model (SM) processes which have not been probed so far. In this work, we evaluate the challenges and the opportunities of the CMS Open Data project in the view of cross-section measurements. In particular, we reevaluate SM cross sections of the production of W bosons, Z bosons, top-quark pairs and WZ dibosons in several decay channels at a center of mass energy of 8 TeV with a corresponding integrated luminosity of 1.8 fb-1. Those cross sections have been previously measured by the ATLAS and CMS collaborations and hence can be used to validate our analysis and calibration strategy. This gives an indication to which precision also new, so far unmeasured cross sections can be determined using CMS Open Data by scientists, who are not a member of the LHC collaborations and hence lack detailed knowledge on experimental and detector related effects and their handling.

hep-ex↗

FASER's Physics Reach for Long-Lived Particles

FASER,the ForwArd Search ExpeRiment,is a proposed experiment dedicated to searching for light, extremely weakly-interacting particles at the LHC. Such particles may be produced in the LHC's high-energy collisions and travel long distances through concrete and rock without interacting. They may then decay to visible particles in FASER, which is placed 480 m downstream of the ATLAS interaction point. In this work we briefly describe the FASER detector layout and the status of potential backgrounds. We then present the sensitivity reach for FASER for a large number of long-lived particle models, updating previous results to a uniform set of detector assumptions, and analyzing new models. In particular, we consider all of the renormalizable portal interactions, leading to dark photons, dark Higgs bosons, and heavy neutral leptons (HNLs); light B-L and $L_i - L_j$ gauge bosons; axion-like particles (ALPs) that are coupled dominantly to photons, fermions, and gluons through non-renormalizable operators; and pseudoscalars with Yukawa-like couplings. We find that FASER and its follow-up, FASER 2, have a full physics program, with discovery sensitivity in all of these models and potentially far-reaching implications for particle physics and cosmology.

hep-ph↗

Electroweak Precision Tests of the Standard Model after the Discovery of the Higgs Boson

The global fit of the Standard Model predictions to electroweak precision data, which has been routinely performed in the past decades by several groups, led to the prediction of the top quark and the Higgs boson masses before their respective discoveries. With the measurement of the Higgs boson mass at the Large Hadron Collider (LHC) in 2012 by the ATLAS and CMS collaborations, the last free parameter of the Standard Model of particle physics has been fixed, and the global electroweak fit can be used to test the full internal consistency of the electroweak sector of the Standard Model and constrain models beyond. In this article, we review the current state-of-the-art theoretical calculations, as well as the precision measurements performed at the LHC, and interpret them within the context of the global electroweak fit. Special focus is drawn in the impact of the Higgs boson mass on the fit.

hep-ph↗

FASER: ForwArd Search ExpeRiment at the LHC

FASER, the ForwArd Search ExpeRiment, is a proposed experiment dedicated to searching for light, extremely weakly-interacting particles at the LHC. Such particles may be produced in the LHC's high-energy collisions in large numbers in the far-forward region and then travel long distances through concrete and rock without interacting. They may then decay to visible particles in FASER, which is placed 480 m downstream of the ATLAS interaction point. In this work, we describe the FASER program. In its first stage, FASER is an extremely compact and inexpensive detector, sensitive to decays in a cylindrical region of radius R = 10 cm and length L = 1.5 m. FASER is planned to be constructed and installed in Long Shutdown 2 and will collect data during Run 3 of the 14 TeV LHC from 2021-23. If FASER is successful, FASER 2, a much larger successor with roughly R ~ 1 m and L ~ 5 m, could be constructed in Long Shutdown 3 and collect data during the HL-LHC era from 2026-35. FASER and FASER 2 have the potential to discover dark photons, dark Higgs bosons, heavy neutral leptons, axion-like particles, and many other long-lived particles, as well as provide new information about neutrinos, with potentially far-ranging implications for particle physics and cosmology. We describe the current status, anticipated challenges, and discovery prospects of the FASER program.

hep-ex↗

Technical Proposal for FASER: ForwArd Search ExpeRiment at the LHC

FASER is a proposed small and inexpensive experiment designed to search for light, weakly-interacting particles during Run 3 of the LHC from 2021-23. Such particles may be produced in large numbers along the beam collision axis, travel for hundreds of meters without interacting, and then decay to standard model particles. To search for such events, FASER will be located 480 m downstream of the ATLAS IP in the unused service tunnel TI12 and be sensitive to particles that decay in a cylindrical volume with radius R=10 cm and length L=1.5 m. FASER will complement the LHC's existing physics program, extending its discovery potential to a host of new, light particles, with potentially far-reaching implications for particle physics and cosmology. This document describes the technical details of the FASER detector components: the magnets, the tracker, the scintillator system, and the calorimeter, as well as the trigger and readout system. The preparatory work that is needed to install and operate the detector, including civil engineering, transport, and integration with various services is also presented. The information presented includes preliminary cost estimates for the detector components and the infrastructure work, as well as a timeline for the design, construction, and installation of the experiment.

physics.ins-det↗

High magnetic fields for fundamental physics

Various fundamental-physics experiments such as measurement of the birefringence of the vacuum, searches for ultralight dark matter (e.g., axions), and precision spectroscopy of complex systems (including exotic atoms containing antimatter constituents) are enabled by high-field magnets. We give an overview of current and future experiments and discuss the state-of-the-art DC- and pulsed-magnet technologies and prospects for future developments.

physics.ins-det↗

Design, Construction and Performance Tests of a Prototype MicroMegas Chamber with Two Readout Planes in a Common Gas Volume

In this paper, the design and the performance of a prototype detector based on MicroMegas technology with two detection planes in a common gas volume is discussed. The detector is suited for the forward region of LHC detectors, addressing the high-rate environment and limited available space. Each detection plane has an active area of 9x9 cm^2 with a two-dimensional strip readout and is separated by a common gas region with a height of 14 mm. A micro-mesh, working as a cathode, is placed in the middle of the common gas volume separating it into two individual cells. This setup allows for an angle reconstruction of incoming particles with a precision of 2 mrad. Since this design reduces the impact of multiple scattering effects by the reduced material budget, possible applications for low energy beam experiments can be envisioned. The performance of the prototype detector has been tested with a 4.4 GeV electron beam, provided by the test beam facility at DESY.

physics.ins-det↗

Determination of the muonic branching ratio of the W boson and its total width via cross-section measurements at the Tevatron and LHC

The total $W$-boson decay width $Γ_W$ is an important observable which allows testing of the standard model. The current world average value is based on direct measurements of final state kinematic properties of $W$-boson decays, and has a relative uncertainty of 2%. The indirect determination of $Γ_W$ via the cross-section measurements of vector-boson production can lead to a similar accuracy. The same methodology leads also to a determination of the leptonic branching ratio. This approach has been successfully pursued by the CDF and D0 experiments at the Tevatron collider, as well as by the CMS collaboration at the LHC. In this paper we present for the first time a combination of the available measurements at hadron colliders, accounting for the correlations of the associated systematic uncertainties. Our combination leads to values of $\textrm{BR}(W\rightarrowμν)=(10.72 \pm 0.16)\%$ and $Γ_W = 2113 \pm 31$ MeV, respectively, both compatible with the current world averages.

hep-ex↗

Determination of the Transverse Momentum of W Bosons in Hadronic Collisions via Forward Folding Techniques

The measurement of the transverse momentum of W bosons in hadron collisions provides not only an important test of QCD calculations, but also is an important input for the precision measurement of the W boson mass. While the measurement of the Z boson transverse momentum is experimentally well under control, the available unfolding techniques for the W boson final states lead generically to relatively large uncertainties. In this paper, we present a new methodology to estimate the W boson transverse momentum spectrum, significantly improving the systematic uncertainties of current approaches.

hep-ex↗

Construction of two large-size four-plane micromegas detectors

We report on the construction and initial performance studies of two micromegas detector quadruplets with an area of 0.5 m$^2$. They serve as prototypes for the planned upgrade project of the ATLAS muon system. Their design is based on the resistive-strip technology and thus renders the detectors spark tolerant. Each quadruplet comprises four detection layers with 1024 readout strips and a strip pitch of 415 $μ$m. In two out of the four layers the strips are inclined by $\pm$1.5$^{\circ}$ to allow for the measurement of a second coordinate. We present the detector concept and report on the experience gained during the detector construction. In addition an evaluation of the detector performance with cosmic rays and test-beam data is given.

physics.ins-det↗

Development and Study of a Micromegas Pad-Detector for High Rate Applications

In this paper, the design and the performance of two prototype detectors based on Micromegas technology with a pad readout geometry is discussed. In addition, two alternative implementations of a spark-resistent protection layer on top of the readout pads have been tested to optimize the charge-up behavior of the detector under high rates. The prototype detectors consist of 500 pads with a size of 5x4 mm, each connected to one independent readout channel, and cover an active area of 10x10 cm. The design of these prototypes and its associated readout infrastructure was developed in such a way that it can be easily adapted for large-size detector concepts.

physics.ins-det↗

Diboson Production in Proton-Proton Collisions at $\sqrt{s}=7$ TeV

This review article summarizes results on the production cross section measurements of electroweak boson pairs ($WW$, $WZ$, $ZZ$, $Wγ$ and $Zγ$) at the Large Hadron Collider (LHC) in $pp$ collisions at a center-of-mass energy of $\sqrt{s}=7$ \TeV. The two general-purpose detectors at the LHC, ATLAS and CMS, recorded an integrated luminosity of $5fb^{-1}$ in 2011, which offered the possibility to study the properties of diboson production to high precision. These measurements test predictions of the Standard Model (SM) in a new energy regime and are crucial for the understanding and the measurement of the SM Higgs boson and other new particles. In this review, special emphasis is drawn on the combination of results from both experiments and a common interpretation with respect to state-of-the-art SM predictions.

hep-ex↗

Signal Characteristics of a Resistive-Strip Micromegas Detector with an Integrated Two-Dimensional Readout

In recent years, micropattern gaseous detectors, which comprise a two-dimensional readout structure within one PCB layer, received significant attention in the development of precision and cost-effective tracking detectors in medium and high energy physics experiments. In this article, we present for the first time a systematic performance study of the signal characteristics of a resistive strip micromegas detector with a two-dimensional readout, based on test-beam and X-ray measurements. In particular, comparisons of the response of the two independent readout-layers regarding their signal shapes and signal reconstruction efficiencies are discussed.

physics.ins-det↗

Review of single vector boson production in pp collisions at $\sqrt{s} = 7$ TeV

This review summarises the main results on the production of single vector bosons in the Standard Model, both inclusively and in association with light and heavy flavour jets, at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of 7 TeV. The general purpose detectors at this collider, ATLAS and CMS, each recorded an integrated luminosity of $\approx 40\,{\rm pb^{-1}}$ and $5\,{\rm fb^{-1}}$ in the years 2010 and 2011, respectively. The corresponding data offer the unique possibility to precisely study the properties of the production of heavy vector bosons in a new energy regime. The accurate understanding of the Standard Model is not only crucial for searches of unknown particles and phenomena but also to test predictions of perturbative Quantum-Chromo-Dynamics calculations and for precision measurements of observables in the electroweak sector. Results from a variety of measurements in which single W or Z bosons are identified are reviewed. Special emphasis in this review is given to interpretations of the experimental results in the context of state-of-the-art predictions.

hep-ex↗

Development and Performance of spark-resistant Micromegas Detectors

The Muon ATLAS MicroMegas Activity (MAMMA) focuses on the development and testing of large-area muon detectors based on the bulk-Micromegas technology. These detectors are candidates for the upgrade of the ATLAS Muon System in view of the luminosity upgrade of Large Hadron Collider at CERN (sLHC). They will combine trigger and precision measurement capability in a single device. A novel protection scheme using resistive strips above the readout electrode has been developed. The response and sparking properties of resistive Micromegas detectors were successfully tested in a mixed (neutron and gamma) high radiation field, in a X-ray test facility, in hadron beams, and in the ATLAS cavern. Finally, we introduced a 2-dimensional readout structure in the resistive Micromegas and studied the detector response with X-rays.

physics.ins-det↗

First Results of the Full-Scale OSQAR Photon Regeneration Experiment

Recent intensive theoretical and experimental studies shed light on possible new physics beyond the standard model of particle physics, which can be probed with sub-eV energy experiments. In the second run of the OSQAR photon regeneration experiment, which looks for the conversion of photon to axion (or Axion-Like Particle), two spare superconducting dipole magnets of the Large Hadron Collider (LHC) have been used. In this paper we report on first results obtained from a light beam propagating in vacuum within the 9 T field of two LHC dipole magnets. No excess of events above the background was detected and the two-photon couplings of possible new scalar and pseudo-scalar particles could be constrained.

hep-ex↗

Determination of Integrated Luminosity via W and Z Boson Production with the ATLAS Detector

The possibility to determine the recorded integrated luminosity via the measurements of the W and Z boson production cross-sections with the ATLAS detector is discussed. The current results based on 2010 data are briefly summarized. Special attention is drawn to theoretical uncertainties of the measurement. The latter give a large contribution to the systematic uncertainties of the measurements. An outlook on the expected precision of an analysis based on 1fb-1 is given and the implications on a possible luminosity determination are discussed.

hep-ex↗

Z boson transverse momentum spectrum from the lepton angular distributions

In view of recent discussions concerning the possibly limiting energy resolution systematics on the measurement of the Z boson transverse momentum distribution at hadron colliders, we propose a novel measurement method based on the angular distributions of the decay leptons. We also introduce a phenomenological parametrization of the transverse momentum distribution that adapts well to all currently available predictions, a useful tool to quantify their differences.

hep-ex↗