53 research outputs found
Reconstructing axion-like particles from beam dumps with simulation-based inference
Axion-like particles (ALPs) that decay into photon pairs pose a challenge for
experiments that rely on the construction of a decay vertex in order to search
for long-lived particles. This is particularly true for beam-dump experiments,
where the distance between the unknown decay position and the calorimeter can
be very large. In this work we use machine learning to explore the possibility
to reconstruct the ALP properties, in particular its mass and lifetime, from
such inaccurate observations. We use a simulation-based inference approach
based on conditional invertible neural networks to reconstruct the posterior
probability of the ALP parameters for a given set of events. We find that for
realistic angular and energy resolution, such a neural network significantly
outperforms parameter reconstruction from conventional high-level variables
while at the same time providing reliable uncertainty estimates. Moreover, the
neural network can quickly be re-trained for different detector properties,
making it an ideal framework for optimizing experimental design.Comment: 34 pages, 18 figures, code available at
https://github.com/amorandini/SBI_axio
Belle II sensitivity to long–lived dark photons
In this letter we point out that the Belle II experiment has a unique sensitivity to visibly decaying long-lived dark photons. Concentrating on the signatures with a single high-energy photon in association with a displaced pair of charged particles, we find that Belle II will be able to probe large regions of parameter space that cannot be covered by any other running or proposed experimental facility. While the signature with charged muons or pions in the final state is expected to be background-free after all selections are applied, the case of final state electrons is more involved and requires an in-depth study. We discuss possible ways to further suppress backgrounds and the corresponding experimental prospects
Real-time Graph Building on FPGAs for Machine Learning Trigger Applications in Particle Physics
We present a design methodology that enables the semi-automatic generation of
a hardware-accelerated graph building architectures for locally constrained
graphs based on formally described detector definitions. In addition, we define
a similarity measure in order to compare our locally constrained graph building
approaches with commonly used k-nearest neighbour building approaches. To
demonstrate the feasibility of our solution for particle physics applications,
we implemented a real-time graph building approach in a case study for the
Belle~II central drift chamber using Field-Programmable Gate Arrays~(FPGAs).
Our presented solution adheres to all throughput and latency constraints
currently present in the hardware-based trigger of the Belle~II experiment. We
achieve constant time complexity at the expense of linear space complexity and
thus prove that our automated methodology generates online graph building
designs suitable for a wide range of particle physics applications. By enabling
an hardware-accelerated pre-processing of graphs, we enable the deployment of
novel Graph Neural Networks~(GNNs) in first level triggers of particle physics
experiments.Comment: 18 page
Forecasting dark showers at Belle II
Dark showers from strongly interacting dark sectors that confine at the GeV scale can give rise to novel signatures at ee colliders. In this work, we study the sensitivity of B factory experiments to dark showers produced through an effective interaction arising from a heavy off-shell mediator. We show that a prospective search for displaced vertices from GeV-scale long-lived particles at Belle II can improve the sensitivity to dark showers substantially compared to an existing search at BaBar. We compare the sensitivity of searches for displaced signals to searches for promptly produced resonances at BaBar and KLOE and calculate sensitivity projections for a single-photon search at Belle II to invisible dark showers produced through an effective interaction. The underlying structure of the effective interaction can be resolved at higher-energy experiments, where the mediator can be produced on-shell. To study the resulting constraints, we update electroweak precision bounds on kinetically mixed Z′ bosons and reinterpret a search for low-mass di-muon resonances at LHCb in terms of dark showers. We find that LHCb and Belle II are most sensitive to different particle decay lengths, underscoring the complementarity of LHC and intensity frontier experiments
DELight: a Direct search Experiment for Light dark matter with superfluid helium
To reach ultra-low detection thresholds necessary to probe unprecedentedly
low Dark Matter masses, target material alternatives and novel detector designs
are essential. One such target material is superfluid He which has the
potential to probe so far uncharted light Dark Matter parameter space at
sub-GeV masses. The new ``Direct search Experiment for Light dark matter'',
DELight, will be using superfluid helium as active target, instrumented with
magnetic micro-calorimeters. It is being designed to reach sensitivity to
masses well below 100\,MeV in Dark Matter-nucleus scattering interactions.Comment: IDM2022 proceedings submitted to SciPos
The Full Event Interpretation -- An exclusive tagging algorithm for the Belle II experiment
The Full Event Interpretation is presented: a new exclusive tagging algorithm
used by the high-energy physics experiment Belle II. The experimental setup of
Belle II allows the precise measurement of otherwise inaccessible meson
decay-modes. The Full Event Interpretation algorithm enables many of these
measurements. The algorithm relies on machine learning to automatically
identify plausible meson decay chains based on the data recorded by the
detector. Compared to similar algorithms employed by previous experiments, the
Full Event Interpretation provides a greater efficiency, yielding a larger
effective sample size usable in the measurement.Comment: 11 pages, 7 figures, 1 tabl
Evidence of and search for double-charmonium production in and decays
Using data samples of and
events collected with the Belle detector, a first experimental
search has been made for double-charmonium production in the exclusive decays
, where , , , , and . No significant signal is
observed in the spectra of the mass recoiling against the reconstructed
or except for the evidence of production with a
significance of for . The
measured branching fraction \BR(\Upsilon(1S)\rightarrow J/\psi+\chi_{c1}) is
. The
confidence level upper limits on the branching fractions of the other modes
having a significance of less than are determined. These results are
consistent with theoretical calculations using the nonrelativistic QCD
factorization approach.Comment: 12 pages, 4 figures, 1 table. The fit range was extended to include
X(4160) signal according to referee's suggestions. Other results unchanged.
Paper was accepted for publication as a regular article in Physical Review
Dark sectors 2016 Workshop: community report
This report, based on the Dark Sectors workshop at SLAC in April 2016,
summarizes the scientific importance of searches for dark sector dark matter
and forces at masses beneath the weak-scale, the status of this broad
international field, the important milestones motivating future exploration,
and promising experimental opportunities to reach these milestones over the
next 5-10 years
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