Search

Silicon Photomultipliers (SiPMs) have emerged as leading photon detectors in experimental physics since their introduction in the late 1990s. With performance characteristics superior to those of traditional photodetectors, SiPMs exhibit up to 60% photon detection efficiency, rapid signal rise times, and resistance to magnetic fields. Their solid-state construction enables mass production, compactness, and high spatial resolution, facilitating their integration into a wide range of experimental setups. Although susceptible to radiation damage, mitigation strategies are being studied to allow their reliable operation even in environments with elevated radiation levels. SiPMs excel in detecting low levels of light, making them well suited for applications involving scintillation and Cherenkov light. Their ability to operate effectively at cryogenic temperatures allows the construction of a new class of multi-tons rare event search experiments such as Darkside-20k. Insensitivity to the magnetic field and mitigation of the radiation damages are making SiPMs well-suited to be used in accelerator driven physics such as Cherenkov light detectors for Particle IDentification (PID) in the future Electron Ion Collider (EIC). [ABSTRACT FROM AUTHOR]

We report results for XUV-IR two-photon ionization of Ar, Ne, NO, and O2, where an XUV attosecond pulse train is superimposed with a synchronized IR pulse, obtained at the ATTOLab laser facility using electron–ion coincidence 3D momentum spectroscopy. Temporally resolved photoelectron angular distributions providing angle-resolved time-delays for np ionization of Ar and Ne, achieved by reconstruction of attosecond beating by interference of two-photon transitions through a unified formalism (Joseph et al. in J Phys B At Mol Opt Phys 53:184007, 2020), are summarized. For inner valence XUV-IR dissociative photoionization of NO and O2 molecules, we report electron–ion kinetic energy correlation diagrams and disentangle the dissociative photoionization processes relying on parallel XUV experiments at Synchrotron SOLEIL. For ionization into the NO+( c 3 Π ) ionic state, extending the formalism developed for single-photon ionization, we focus on photoelectron angular distributions averaged on the delay between the XUV and the IR field in the field frame, molecular frame, and electron frame of reference. [ABSTRACT FROM AUTHOR]

PUMA, antiProton Unstable Matter Annihilation, is a nuclear-physics experiment at CERN aiming at probing the surface properties of stable and rare isotopes by use of low-energy antiprotons. Low-energy antiprotons offer a very unique sensitivity to the neutron and proton densities at the annihilation site, i.e. in the tail of the nuclear density. Today, no facility provides a collider of low-energy radioactive ions and low-energy antiprotons: while not being a collider experiment, PUMA aims at transporting one billion antiprotons from ELENA, the Extra-Low-ENergy Antiproton ring, to ISOLDE, the rare-isotope beam facility of CERN. PUMA will enable the capture of low-energy antiprotons by short-lived nuclei and the measurement of the emitted radiations. In this way, PUMA will give access to the so-far largely unexplored isospin composition of the nuclear-radial-density tail of radioactive nuclei. The motivations, concept and current status of the PUMA experiment are presented. [ABSTRACT FROM AUTHOR]

The small binding energy of the hypertriton leads to predictions of the non-existence of bound hypernuclei for isotriplet three-body systems such as nn Λ. However, invariant mass spectroscopy at GSI has reported events that may be interpreted as the bound nn Λ state. The nn Λ state was sought by missing-mass spectroscopy via the (e, e ′ K +) reaction at Jefferson Lab's experimental Hall A. The present experiment has higher sensitivity to the nn Λ-state investigation in terms of better precision by a factor of about three. The analysis shown in this article focuses on the derivation of the reaction cross-section for the 3H(γ*, K +)X reaction. Events that were detected in an acceptance, where a Monte Carlo simulation could reproduce the data well (⁠|$|\delta p/p| \lt 4\%$|⁠), were analyzed to minimize the systematic uncertainty. No significant structures were observed with the acceptance cuts, and the upper limits of the production cross-section of the nn Λ state were obtained to be 21 and |$31 \, \rm {nb} \, \rm {sr}^{-1}$| at the |$90\%$| confidence level when theoretical predictions of (− B Λ, Γ) = (0.25, 0.8) MeV and (0.55, 4.7) MeV, respectively, were assumed. The cross-section result provides valuable information for examining the existence of nn Λ. [ABSTRACT FROM AUTHOR]

Recent development of ultrafast measurement techniques on the sub-femtosecond time scale has enabled us to see the atom–laser interaction in real time. One of the important observables to study the temporally resolved dynamics is the various time delay in the process. Time delays is an experimentally measurable quantity, where the time is not. Time delays in quantum collisions and in photoionization/photodetachment of atomic and molecular systems is reviewed. The formalisms of time delay in the context of quantum collisions by Eisenbud and Wigner that by Smith and their equivalence is discussed. The time-reversal symmetry between solutions with outgoing and ingoing wave boundary conditions allow us to interpret photoionization/photodetachment as half-scattering. Subsequently, the formalism of Eisenbud–Wigner–Smith time delay is extended in photoionization/photodetachment from collisions. We discuss that the time delay can be written as a self-adjoint quantum operator which depicts its measurability. On the experimental side, the measurement protocols are reviewed for attosecond streaking and RABBITT. Along with the EWS time delay, the measurement introduces an additional (which is negative) time delay. From the measurement of total delay and an analytical/numerical estimate of the measurement induced part, one gets the EWS time delay in the process. A few illustrative examples of studies on time delay are given to get a flavour of the outstanding advances made in this field in the last two decades. [ABSTRACT FROM AUTHOR]

It is remarkable that time delay is an experimentally measurable quantity, but time itself is not. Time delay in quantum collisions and in photoionisation/photodetachment of atomic and molecular systems is reviewed in this paper. Wigner–Eisenbud formalism of time delay in quantum collision of a wavepacket with a target is discussed. Its equivalence with Smith's formalism of time delay, based on an independent basis for time delay in terms of excess particle density in the collision zone, is demonstrated. Similarity and difference between quantum collision of an electron with a positive atomic/molecular ion and photoionisation/photodetachment of a neutral atom/molecule are discussed, and the underlying quantum dynamics involving the time-reversal symmetry between solutions with outgoing and ingoing wave boundary conditions is pointed out to interpret photoionisation/photodetachment as half-scattering. This relationship is subsequently taken advantage to extend the formalism of Wigner–Eisenbud–Smith time delay in photoionisation/photodetachment. The measurability of time delay is accounted for in terms of a self-adjoint quantum operator that characterises it, even if there is no such operator for time itself. A few illustrative examples of theoretical and experimental studies of time delay are given to indicate outstanding advances made in this field in the last two decades. [ABSTRACT FROM AUTHOR]

The long-standing scientific quest of real-time tracing electronic motion and dynamics in all states of matter has been remarkably benefited by the development of intense laser-based pulsed sources with a temporal resolution in the attosecond [1 attosecond = 10−18 s] time scale. Nowadays, attosecond pulses are routinely produced in laboratories by the synthesis of the frequency components of broadband coherent extreme ultraviolet (XUV) radiation generated by the interaction of matter with intense femtosecond (fs) pulses. Attosecond pulse metrology aims at the accurate and complete determination of the temporal and phase characteristics of attosecond pulses and is one of the most innovative challenges in the broad field of ultrashort pulse metrology. For more than two decades since coherent high-brilliance broadband XUV sources have become available, fascinating advances in attosecond pulse metrology have led to the development of remarkable techniques for pulse duration measurements as well as the complete reconstruction of those pulses. Nonetheless, new challenges born from diverse fields call upon for additional efforts and continuously innovative ideas in the field. In this perspective article, we follow the history of ultrashort pulse technology tracing attosecond pulse production and characterization approaches, focus on the operation principles of the most commonly used techniques in the region where they interact with matter, address their limitations, and discuss future prospects as well as endeavors of the field to encounter contemporary scientific progress. [ABSTRACT FROM AUTHOR]

In this tutorial, we provide a short review of attosecond pulse characterization techniques and a pedagogical account of a recently proposed method called Pulse Analysis by Delayed Absorption (PANDA) [S. Pabst and J. M. Dahlström, Phys. Rev. A 94, 013411 (2016)]. We discuss possible implementations of PANDA in alkali atoms using either principal quantum number wave packets or spin-orbit wave packets. The main merit of the PANDA method is that it can be used as a pulse characterization method that is free from atomic latency effects, such as scattering phase shifts and long-lived atomic resonances. Finally, we propose that combining the PANDA method with angle-resolved photoelectron detection should allow for experimental measurements of attosecond delays in photoionization from bound wave packets on the order of tens of attoseconds. [ABSTRACT FROM AUTHOR]

Photoionization by an eXtreme UltraViolet (XUV) attosecond pulse train (APT) in the presence of an infrared pulse (RABBITT method) conveys information about the atomic photoionization delay. By taking the difference of the spectral delays between pairs of rare gases (Ar,He), (Kr,He) and (Ne,He) it is possible to eliminate in each case the larger group delay (‘attochirp’) associated with the APT itself and obtain the Ar, Kr and Ne Wigner delays referenced to model calculations of the He delay. In this work we measure how the delays vary as a function of XUV photon energy but we cannot determine the absolute delay difference between atoms due to lack of precise knowledge of the initial conditions. The extracted delays are compared with several theoretical predictions and the results are consistent within 30 as over the energy range from 10 to 50 eV. An ‘effective’ Wigner delay over all emission angles is found to be more consistent with our angle-integrated measurement near the Cooper minimum in Ar. We observe a few irregular features in the delay that may be signatures of resonances. [ABSTRACT FROM AUTHOR]