In a 2016 paper, an anomaly in the internal pair creation on the
M1
transition depopulating the 18.15 MeV isoscalar 1+ state on 8Be was observed. This could be explained by the creation and ...subsequent decay of a new boson, with mass
m
X
c
2
= 16.70 MeV. Further experiments of the same transition with an improved and independent setup were performed, which constrained the mass of the X17 boson (
m
X
c2) and its branching ratio relative to the γ-decay of the 8Be excited state (
B
X
), to
m
X
c
2
= 17.01(16) MeV and
B
X
= 6(1) 10−6, respectively. Using the latter setup, the
e
+
e
− pairs depopulating the 21 MeV
J
π = 0
−
0
+
transition in 4He were investigated and a resonance in the angular correlation of the pairs was observed, which could be explained by the same X17 particle, with mass
m
X
c
2
= 16.98 ± 0.16(stat) ± 0.20(syst) MeV.
An electron–positron pair spectrometer has been designed and constructed for the simultaneous measurement of energy- and angular correlations of e+e- pairs. Experimental results are obtained over a ...wide angular range for high-energy transitions in 16O, 12C and 8Be. The results showed that the angular correlations between 50 and 180°of the e+e- pairs in the energy range between 6 and 18MeV can be determined with sufficient resolution and efficiency in good agreement with the GEANT simulations.
Recently, we observed an anomalous peak-like excess of internal e+e− pairs at around 140° for the M1 transition depopulating the 18.15 MeV isoscalar 1+ state in 8Be. The deviation from the ...theoretical prediction can be described by GEANT simulations assuming the creation and subsequent decay of a new, light boson with a mass of 16.7 MeV/c2. In order to reduce the possible systematic errors from the experimenntal data, we re-investigated the 8Be anomaly with an improved setup and confirmed the anomaly within the statistical uncertainties. We also studied the angular correlation of the electron-positron pairs created in the M0 transition depopulating the 21.01 MeV 0− state in 4He, and observed an anomalous excess of e+e− pairs at a significantly smaller angle of 115°. Since the transition energy was higher in this case, the observed anomaly could be described by assuming the creation and subsequent decay of the same light particle in the simulations.
A new light particle is being born Krasznahorkay, A.J.; Begala, M.; Csatlós, M. ...
Journal of physics. Conference series,
12/2022, Letnik:
2391, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
A few years ago we observed anomalous electron-positron angular correlations for the 18.15 MeV M1 transition of
8
Be. This was interpreted as the creation and decay of an intermediate ...bosonic particle with a mass of
m
0
c
2
=16.70±0.35(stat )±0.5(sys) MeV, which is now called X17. The possible relation of the X17 boson to the dark matter problem triggered an enormous interest in the wider physics community. We also observed a similar anomaly in
4
He, which could be described also by the creation and subsequent decay of the same X17 particle. Very recently, the
11
B proton capture reaction was used for exciting the 17.2 MeV broad (Γ=1.15 MeV) resonance in
12
C and studying their internal pair creation decay. Anomalies were observed in the angular correlation of the electron-positron pairs, which together with the
8
Be and
4
He data provides kinematic evidence for the X17 particle and supports their vector boson and fifth force explanation.
Abstract
A detailed geometry description is essential to any high quality track reconstruction application. In current C++ based track reconstruction software libraries this is often achieved by an ...object oriented, polymorphic geometry description that implements different shapes and objects by extending a common base class. Such a design, however, has been shown to be problematic when attempting to adapt these applications to run on heterogeneous computing hardware, particularly on hardware accelerators. We present detray, a compile time polymorphic and yet accurate track reconstruction geometry description which is part of the ACTS parallelization R&D effort. detray is built as an index based geometry description with a shallow memory layout, that uses variadic template programming to allow custom shapes and intersection algorithms rather than inheritance from abstract base classes. It is designed to serve as a potential geometry and navigation backend for ACTS and as such implements the ACTS navigation model of boundary portals and purely surface based geometric entities. detray is designed to work with a dedicated memory management library and thus can be instantiated as a geometry model in host and device code.
Abstract
Programmers using the C++ programming language are increasingly taught to manage memory implicitly through containers provided by the C++ standard library. However, heterogeneous programming ...platforms often require explicit allocation and deallocation of memory. This discrepancy in memory management strategies can be daunting and problematic for C++ developers who are not already familiar with heterogeneous programming. The C++17 standard introduces the concept of
memory resources
, which allow the user to control how standard library containers allocate memory; we believe that this addition to the C++17 standard is a powerful tool towards the unification of memory management for heterogeneous systems with best-practice C++ development. In this paper, we present
vecmem
, a library of memory resources which allows efficient and user-friendly allocation of memory on CUDA, HIP, and SYCL devices through standard C++ containers. We investigate the design and use cases of such a library, the potential performance gains over naive memory allocation, and the limitations of this memory allocation model.
Abstract
Recently, we observed an anomalous peak-like excess of internal e
+
e
−
pairs at around 140° for the M1 transition depopulating the 18.15 MeV isoscalar 1
+
state in
8
Be. The deviation from ...the theoretical prediction can be described by GEANT simulations assuming the creation and subsequent decay of a new, light boson with a mass of 16.7 MeV/c
2
. In order to reduce the possible systematic errors from the experimenntal data, we re-investigated the
8
Be anomaly with an improved setup and confirmed the anomaly within the statistical uncertainties. We also studied the angular correlation of the electron-positron pairs created in the M0 transition depopulating the 21.01 MeV 0
−
state in
4
He, and observed an anomalous excess of e
+
e
−
pairs at a significantly smaller angle of 115°. Since the transition energy was higher in this case, the observed anomaly could be described by assuming the creation and subsequent decay of the same light particle in the simulations.
The ATLAS experiment, aimed at recording the results of LHC proton-proton collisions, is upgrading its Trigger and Data Acquisition (TDAQ) system during the current LHC first long shutdown. The ...purpose of the upgrade is to add robustness and flexibility to the selection and the conveyance of the physics data, simplify the maintenance of the infrastructure, exploit new technologies and, overall, make ATLAS data-taking capable of dealing with increasing event rates. The TDAQ system used to date is organised in a three-level selection scheme, including a hardware-based first-level trigger and second- and third-level triggers implemented as separate software systems distributed on separate, commodity hardware nodes. While this architecture was successfully operated well beyond the original design goals, the accumulated experience stimulated interest to explore possible evolutions. We will also be upgrading the hardware of the TDAQ system by introducing new elements to it. For the high-level trigger, the current plan is to deploy a single homogeneous system, which merges the execution of the second and third trigger levels, still separated, on a unique hardware node. Prototyping efforts already demonstrated many benefits to the simplified design. In this paper we report on the design and the development status of this new system.
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