63 research outputs found
Energy-dependent polarization of Gamma-Ray Bursts' prompt emission with the POLAR and POLAR-2 instruments
Gamma-Ray Bursts are among the most powerful events in the Universe. Despite
half a century of observations of these transient sources, many open questions
remain about their nature. Polarization measurements of the GRB prompt emission
have long been theorized to be able to answer most of these questions. With the
aim of characterizing the polarization of these prompt emissions, a compact
Compton polarimeter, called POLAR, has been launched to space in September
2016. Time integrated polarization analysis of the POLAR GRB catalog have shown
that the prompt emission is lowly polarized or fully unpolarized. However, time
resolved analysis depicted strong hints of an evolving polarization angle
within single pulses, washing out the polarization degree in time integrated
analyses. Here we will for the first time present energy resolved polarization
measurements with the POLAR data. The novel analysis, performed on several
GRBs, will provide new insights and alter our understanding of GRB
polarization. The analysis was performed using the 3ML framework to fit
polarization parameters versus energy in parallel to the spectral parameters.
Although limited by statistics, the results could provide a very relevant input
to disentangle between existing theoretical models. In order to gather more
statistics per GRB and perform joint time and energy resolved analysis, a
successor instrument, called POLAR-2, is under development with a launch window
early 2025 to the CSS. After presenting the first energy resolved polarization
results of the POLAR mission, we will present the prospects for such
measurements with the upcoming POLAR-2 mission.Comment: Proceeding from the 38th International Cosmic Ray Conference
(ICRC2023), 9 pages, 6 figure
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.Comment: 13 pages, 4 figures, submitted as Input to the European Particle
Physics Strategy Update 2018-2020 and draws on FASER's Letter of Intent,
Technical Proposal, and physics case documents (arXiv:1811.10243,
arXiv:1812.09139, and arXiv:1811.12522
In-Orbit Instrument Performance Study and Calibration for POLAR Polarization Measurements
POLAR is a compact space-borne detector designed to perform reliable
measurements of the polarization for transient sources like Gamma-Ray Bursts in
the energy range 50-500keV. The instrument works based on the Compton
Scattering principle with the plastic scintillators as the main detection
material along with the multi-anode photomultiplier tube. POLAR has been
launched successfully onboard the Chinese space laboratory TG-2 on 15th
September, 2016. In order to reliably reconstruct the polarization information
a highly detailed understanding of the instrument is required for both data
analysis and Monte Carlo studies. For this purpose a full study of the in-orbit
performance was performed in order to obtain the instrument calibration
parameters such as noise, pedestal, gain nonlinearity of the electronics,
threshold, crosstalk and gain, as well as the effect of temperature on the
above parameters. Furthermore the relationship between gain and high voltage of
the multi-anode photomultiplier tube has been studied and the errors on all
measurement values are presented. Finally the typical systematic error on
polarization measurements of Gamma-Ray Bursts due to the measurement error of
the calibration parameters are estimated using Monte Carlo simulations.Comment: 43 pages, 30 figures, 1 table; Preprint accepted by NIM
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.Comment: 82 pages, 62 figures; submitted to the CERN LHCC on 7 November 201
The internal alignment and position resolution of the AMS-02 silicon tracker determined with cosmic-ray muons
Abstract The Alpha Magnetic Spectrometer is a large acceptance cosmic-ray detector ( 0.5 m 2 sr ) designed to operate at an altitude of 400 km on the International Space Station. The AMS-02 silicon tracker contains 2264 silicon microstrip sensors (total active area 6.75 m 2 ). The internal alignment parameters of the assembled tracker have been determined on the ground with cosmic-ray muons. The alignment procedure is described and results for the alignment precision and position resolution are reported
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 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
First Direct Observation of Collider Neutrinos with FASER at the LHC
We report the first direct observation of neutrino interactions at a particle
collider experiment. Neutrino candidate events are identified in a 13.6 TeV
center-of-mass energy collision data set of 35.4 fb using the
active electronic components of the FASER detector at the Large Hadron
Collider. The candidates are required to have a track propagating through the
entire length of the FASER detector and be consistent with a muon neutrino
charged-current interaction. We infer neutrino interactions
with a significance of 16 standard deviations above the background-only
hypothesis. These events are consistent with the characteristics expected from
neutrino interactions in terms of secondary particle production and spatial
distribution, and they imply the observation of both neutrinos and
anti-neutrinos with an incident neutrino energy of significantly above 200 GeV.Comment: Submitted to PRL on March 24 202
The large area detector onboard the eXTP mission
The Large Area Detector (LAD) is the high-throughput, spectral-timing instrument onboard the eXTP mission, a flagship
mission of the Chinese Academy of Sciences and the China National Space Administration, with a large European
participation coordinated by Italy and Spain. The eXTP mission is currently performing its phase B study, with a target
launch at the end-2027. The eXTP scientific payload includes four instruments (SFA, PFA, LAD and WFM) offering
unprecedented simultaneous wide-band X-ray timing and polarimetry sensitivity. The LAD instrument is based on the
design originally proposed for the LOFT mission. It envisages a deployed 3.2 m2 effective area in the 2-30 keV energy
range, achieved through the technology of the large-area Silicon Drift Detectors - offering a spectral resolution of up to
200 eV FWHM at 6 keV - and of capillary plate collimators - limiting the field of view to about 1 degree. In this paper
we will provide an overview of the LAD instrument design, its current status of development and anticipated
performance
First neutrino interaction candidates at the LHC
FASER at the CERN Large Hadron Collider (LHC) is designed to directly
detect collider neutrinos for the first time and study their cross sections at
TeV energies, where no such measurements currently exist. In 2018, a pilot
detector employing emulsion films was installed in the far-forward region of
ATLAS, 480 m from the interaction point, and collected 12.2 fb of
proton-proton collision data at a center-of-mass energy of 13 TeV. We describe
the analysis of this pilot run data and the observation of the first neutrino
interaction candidates at the LHC. This milestone paves the way for high-energy
neutrino measurements at current and future colliders.Comment: Auxiliary materials are available at
https://faser.web.cern.ch/fasernu-first-neutrino-interaction-candidate
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