Coincident Emission Research Articles

A targeted search for FRB counterparts with Konus-Wind

ABSTRACT We present results of the search for hard X-ray/soft gamma-ray emission in coincidence with publicly reported (via Transient Name Server, TNS1) fast radio bursts (FRBs). The search was carried out using continuous Konus-Wind data with 2.944 s time resolution. We perform a targeted search for each individual burst from 581 FRBs, along with a stacking analysis of the bursts from eight repeating sources in our sample and a separate stacking analysis of the bursts from the non-repeating FRBs. We find no significant associations in either case. We report upper bounds on the hard X-ray (20–1500 keV) flux assuming four spectral models, which generally describe spectra of short and long gamma-ray bursts (GRBs), magnetar giant flares, and the short burst, coincident with FRB 200428 from a Galactic magnetar. Depending on the spectral model, our upper bounds are in the range of (0.1–2) × 10−6 erg cm−2. For 18 FRBs with known distances, we present upper bounds on the isotropic equivalent energy release and peak luminosity. For the nearest FRB 200120E, we derive the most stringent upper bounds of Eiso ≤ 2.0 × 1044 erg and Liso ≤ 1.2 × 1044 erg s−1. Furthermore, we report lower bounds on radio-to-gamma-ray fluence ratio Eradio/Eiso ≥ 10−11–10−9 and compare our results with previously reported searches and theoretical predictions for high-energy counterparts to FRBs.

The Spatial and Emission Properties of the Large [O iii] Emission Nebula Near M31

Drechsler et al. reported the unexpected discovery of a 1.°5 long [O iii] emission nebula 1.°2 southeast of the M31 nucleus. Here we present additional images of this large emission arc, called the Strottner–Drechsler–Sainty Object (SDSO), along with radial velocity and flux measurements from low-dispersion spectra. Independent sets of [O iii] images show SDSO to be composed of broad streaks of diffuse emission aligned northeast–southwest. Deep Hα images reveal no strong coincident emission suggesting a high [O iii]/Hα ratio. We also find no other [O iii] emission nebulosity as bright as SDSO within several degrees of M31 and no filamentary Hα emission connected to SDSO. Optical spectra taken along the nebula’s northern limb reveal [O iii] λ λ4959, 5007 emissions matching the location and extent seen in our [O iii] images. The heliocentric velocity of this [O iii] nebulosity is −9.8 ± 6.8 km s−1 with a peak surface brightness of (4 ± 2) × 10−18 erg s−1 cm−2 arcsec−2 (∼0.55 Rayleigh). We discuss SDSO as a possible unrecognized supernova remnant, a large and unusually nearby planetary nebula, a stellar bow shock nebula, or an interaction of M31's outer halo with Local Group circumgalactic gas. We conclude that galactic origins for SDSO are unlikely and favor instead an extragalactic M31 halo–circumgalactic cloud interaction scenario, despite the nebula’s low radial velocity. We then describe new observations that may help resolve the nature and origin of this large nebulosity so close to M31 in the sky.

Blazar Constraints on Neutrino-Dark Matter Scattering.

Neutrino emission in coincidence with gamma rays has been observed from the blazar TXS 0506+056 by the IceCube telescope. Neutrinos from the blazar had to pass through a dense spike of dark matter (DM) surrounding the central black hole. The observation of such a neutrino implies new upper bounds on the neutrino-DM scattering cross section as a function of DM mass. The constraint is stronger than existing ones for a range of DM masses, if the cross section rises linearly with energy. For constant cross sections, competitive bounds are also possible, depending on details of the DM spike.

Signatures of cooperative emission in photon coincidence: Superradiance versus measurement-induced cooperativity

Indistinguishable quantum emitters confined to length scales smaller than the wavelength of the light become superradiant. Compared to uncorrelated and distinguishable emitters, superradiance results in qualitative modifications of optical signals such as photon coincidences. However, recent experiments revealed that similar signatures can also be obtained in situations where emitters are too far separated to be superradiant if correlations between emitters are induced by the wave-function collapse during an emission-angle-selective photon detection event. Here, we compare two sources for cooperative emission, superradiance and measurement-induced cooperativity, and analyze their impact on time-dependent optical signals. We find that an antidip in photon coincidences at zero time delay is a signature of interemitter correlations in general but does not unambiguously prove the presence of superradiance. This suggests that photon coincidences at zero time delay alone are not sufficient and time-dependent data are necessary to clearly demonstrate a superradiant enhancement of the spontaneous radiative decay rate.

Hong–Ou–Mandel sensing via superradiant coupling of discrete fluorescent emitters

The Hong–Ou–Mandel (HOM) effect is a fascinating quantum phenomenon that defies classical explanation. Traditionally, remote nonlinear sources have been used to achieve coincident photons at the HOM beam splitter. Here, we suggest that the coincident emission source required for HOM interference can be created locally using superradiant near field coupled emitters positioned across the beam splitter gap. We show that sensitivity to permittivity changes in the beam splitter gap, and corresponding Fisher information can be substantially enhanced with HOM photon detection. Subsequently, we outline several strategies for integration of superradiant emitters with practical sensor systems. Taken together, these findings should pave a way for a wide array of near field HOM quantum sensors and novel quantum devices.

AGILE Observations of Fast Radio Bursts

Abstract We report on a systematic search for hard X-ray and γ-ray emission in coincidence with fast radio bursts (FRBs) observed by the AGILE satellite. We used 13 yr of AGILE archival data searching for time coincidences between exposed FRBs and events detectable by the MCAL (0.4–100 MeV) and GRID (50 MeV–30 GeV) detectors at timescales ranging from milliseconds to days/weeks. The current AGILE sky coverage allowed us to extend the search for high-energy emission preceding and following the FRB occurrence. We considered all FRB sources currently included in catalogs and identified a subsample (15 events) for which a good AGILE exposure with either MCAL or GRID was obtained. In this paper we focus on nonrepeating FRBs, compared to a few nearby repeating sources. We did not detect significant MeV or GeV emission from any event. Our hard X-ray upper limits (ULs) in the MeV energy range were obtained for timescales from submillisecond to seconds, and in the GeV range from minutes to weeks around event times. We focus on a subset of five nonrepeating and two repeating FRB sources whose distances are most likely smaller than that of 180916.J0158+65 (150 Mpc). For these sources, our MeV ULs translate into ULs on the isotropically emitted energy of about 3 × 1046 erg, comparable to that observed in the 2004 giant flare from the Galactic magnetar SGR 1806–20. On average, these nearby FRBs emit radio pulses of energies significantly larger than the recently detected SGR 1935+2154 and are not yet associated with intense MeV flaring.

A high-resolution [formula omitted] coincidence spectrometry system for radioxenon measurements

GBL15, the UK’s noble gas certified Comprehensive Nuclear-Test-Ban Treaty (CTBT) radionuclide laboratory supports the International Monitoring System (IMS) through measurement of environmental radioxenon samples using β−γ coincidence spectrometry. GBL15 currently utilises a system comprised of NaI(Tl) γ-detectors and plastic scintillator β-detectors to measure coincident emissions from the four radioxenon isotopes of interest: 133Xe, 135Xe, 131mXe and 133mXe. This paper reports on the setup, calibration and assessment of the CEA/Mirion-developed PIPSBox, used in coincidence setup with a high-purity germanium detector. The system has been configured to measure the signals from the four radionuclides of interest and demonstrates improved discrimination between signals and less interference compared to the current system. The coincident detection efficiencies are quantified through measurement of spiked radioxenon samples.

Observation of an Inversion in Photophysical Tuning in a Systematic Study of Luminescent Triazole-Based Osmium(II) Complexes.

In a systematic survey of luminescent bis(terdentate) osmium(II) complexes, a tipping point involving a reversal in photophysical tuning is observed whereby increasing stabilization of the ligand-based lowest unoccupied molecular orbital (LUMO) results in a blue shift in the optical absorption and emission bands. The complexes [Os(N^N'^N″)2]2+ [N^N'^N″ = 2,6-bis(1-phenyl-1,2,3-triazol-4-yl)pyridine (Os1), 2,6-bis(1-benzyl-1,2,3-triazol-4-yl)pyrazine (Os2), 6-(1-benzyl-1,2,3-triazol-4-yl)-2,2'-bipyridyl (Os3), 2-(pyrid-2-yl)-6-(1-benzyl-1,2,3-triazol-4-yl)pyrazine (Os4), 2-(pyrazin-2-yl)-6-(1-benzyl-1,2,3-triazol-4-yl)pyridine (Os5), and 6-(1-benzyl-1,2,3-triazol-4-yl)-2,2'-bipyrazinyl (Os6)] have been prepared and characterized, and all complexes display phosphorescence ranging from the orange to near-IR regions of the spectrum. Replacement of the central pyridine in the ligands of Os1 by the more π-accepting pyrazine in Os2 results in a 55 nm red shift in the triplet metal-to-ligand charge-transfer-based emission band, while a larger red shift of 107 nm is observed for the replacement of one of the triazole donors in the ligands of Os1 by a second pyridine ring in Os3 (λemmax = 702 nm). Interestingly, replacement of the central pyridine ring in the ligands of Os3 by pyrazine (Os4,λemmax = 702 nm) fails to result in a further red shift in the emission band. Reversal of the relative positions of the pyridine and pyrazine donors in Os5 (λemmax = 733 nm) compared to Os4 does indeed result in the expected red shift in the emission with respect to that for Os3 based on the increased π-acceptor character of the ligands present. However, an inversion in emission tuning is observed for Os6, in which the incorporation of a second pyrazine donor in the ligand architecture results in a blue shift in the optical absorption and emission maxima (λemmax = 710 nm). Electrochemical studies reveal that while incorporating pyrazine in the ligands indeed results in an expected anodic shift in the first reduction potential through stabilization of the ligand-based LUMO, there is also a concomitant anodic shift in the OsII/OsIII-based oxidation potential. This stabilization of the metal-based highest occupied molecular orbital (HOMO) thus nullifies the effect of stabilization of the LUMO in Os4 compared to Os3, resulting in these complexes having coincident emission maxima. For Os6, stabilization of the HOMO through the incorporation of two pyrazine donors in the ligand structure now exceeds stabilization of the LUMO, resulting in a larger HOMO-LUMO gap and a counterintuitive blue shift in the optical properties in comparison with those of Os5. While it is known that the replacement of ligands (e.g., replacing bipyridyl with bipyrazinyl) can result in a larger HOMO-LUMO energy gap through greater stabilization of the HOMO, these results importantly allow us to capture the tipping point at which this inversion in photophysical tuning occurs. This therefore enables us to explore the limits available in emission tuning with a relatively simple and minimalist ligand structure.

A potential progenitor for the Type Ic supernova 2017ein

We report the first detection of a credible progenitor system for a Type Ic supernova (SN Ic), SN 2017ein. We present spectra and photometry of the SN, finding it to be similar to carbon-rich, low-luminosity SNe Ic. Using a post-explosion Keck adaptive optics image, we precisely determine the position of SN 2017ein in pre-explosion \hst\ images, finding a single source coincident with the SN position. This source is marginally extended, and is consistent with being a stellar cluster. However, under the assumption that the emission of this source is dominated by a single point source, we perform point-spread function photometry, and correcting for line-of-sight reddening, we find it to have $M_{\rm F555W} = -7.5\pm0.2$ mag and $m_{\rm F555W}-m_{\rm F814W}$=$-0.67\pm0.14$ mag. This source is bluer than the main sequence and brighter than almost all Wolf-Rayet stars, however it is similar to some WC+O- and B-star binary systems. Under the assumption that the source is dominated by a single star, we find that it had an initial mass of $55\substack{+20-15} M_{\odot}$. We also examined binary star models to look for systems that match the overall photometry of the pre-explosion source and found that the best-fitting model is a $80$+$48 M_{\odot}$ close binary system in which the $80 M_{\odot}$ star is stripped and explodes as a lower mass star. Late-time photometry after the SN has faded will be necessary to cleanly separate the progenitor star emission from the additional coincident emission.

Measurement of mass-gated neutron multiplicity for the Ti48+Pb208 reaction at 57.4 MeV excitation energy

The neutron emission in coincidence with the fragments have been investigated for the $^{48}\mathrm{Ti}+^{208}\mathrm{Pb}$ reaction populating the near superheavy compound nucleus $^{256}\mathrm{Rf}$ at an excitation energy of 57.4 MeV. The National Array of Neutron Detectors facility is used for a precise determination of the prescission (${M}_{n}^{\mathrm{pre}}$) and postscission (${M}_{n}^{\mathrm{post}}$) neutron multiplicities as a function of fission observables. A moving source fitting procedure has been adopted to deduce ${M}_{n}^{\mathrm{pre}}$ and ${M}_{n}^{\mathrm{post}}$. The variation of ${M}_{n}^{\mathrm{pre}}$ with the mass-split and total kinetic energy (TKE) of the fission fragments have been studied to understand the fission dynamics of $^{256}\mathrm{Rf}$. It is observed that ${M}_{n}^{\mathrm{pre}}$ increases from the value of 1.66 $\ifmmode\pm\else\textpm\fi{}$ 0.07 to 2.23 $\ifmmode\pm\else\textpm\fi{}$ 0.07 with transition from the asymmetric to the symmetric mass region. ${M}_{n}^{\mathrm{pre}}$ is also found to increase with the decrease in TKE, which is probably due to the neutron emission during the acceleration time of the fission fragments in this heavy system. The experimental results for neutron multiplicity have also been compared with the theoretical predictions from the statistical model calculations. From this comparison, the value of reduced dissipation strength for the $^{256}\mathrm{Rf}$ nucleus is found to be (13.0 $\ifmmode\pm\else\textpm\fi{}$ 1.0) $\ifmmode\times\else\texttimes\fi{} {10}^{21} {\mathrm{s}}^{\ensuremath{-}1}$ and a fission delay time of (${67.3}_{\ensuremath{-}3.9}^{+5.3}$) $\ifmmode\times\else\texttimes\fi{} {10}^{\ensuremath{-}21}$ s has also been estimated. For the spontaneous fission of $^{256}\mathrm{Rf}$, the extracted average neutron multiplicity ${M}_{n}^{sf}$ is found to be 4.4 $\ifmmode\pm\else\textpm\fi{}$ 1.0 which is in good agreement with the recently reported value for the $^{258,260}\mathrm{Rf}$ isotopes.

Optical emission associated with the Galactic supernova remnant G179.0+2.6

Narrow passband optical images of the large Galactic supernova remnant G179.0+2.6 reveal a faint but nearly complete emission shell dominated by strong [O III] 4959,5007 A line emission. The remnant's optical emission, which consists of both diffuse and filamentary features, is brightest along its southern and northeastern limbs. Deep H-alpha images detect little coincidence emission indicating an unusually high [O III]/H-alpha emission ratio for such a large and apparently old remnant. Low-dispersion optical spectra of several regions confirm large [O III]/H-alpha line ratios with typical values around 10. The dominance of [O III] emission for the majority of the remnant's optical filaments suggests shock velocities above 100 km/s are present throughout most of the remnant, likely reflecting a relatively low density ambient ISM. The remnant's unusually strong [O III] emission adds to the remnant's interesting set of properties which include a thick radio emission shell, radial polarization of its radio emission like that typically seen in young supernova remnants, and an unusually slow-rotating gamma-ray pulsar with a characteristic spin-down age ~50 kyr.

Calibration of 4π NaI(Tl) detectors with coincidence summing correction using new numerical procedure and ANGLE4 software

The 4π NaI(Tl) γ-ray detectors are consisted of the well cavity with cylindrical cross section, and the enclosing geometry of measurements with large detection angle. This leads to exceptionally high efficiency level and a significant coincidence summing effect, much more than a single cylindrical or coaxial detector especially in very low activity measurements. In the present work, the detection effective solid angle in addition to both full-energy peak and total efficiencies of well-type detectors, were mainly calculated by the new numerical simulation method (NSM) and ANGLE4 software. To obtain the coincidence summing correction factors through the previously mentioned methods, the simulation of the coincident emission of photons was modeled mathematically, based on the analytical equations and complex integrations over the radioactive volumetric sources including the self-attenuation factor. The measured full-energy peak efficiencies and correction factors were done by using 152Eu, where an exact adjustment is required for the detector efficiency curve, because neglecting the coincidence summing effect can make the results inconsistent with the whole. These phenomena, in general due to the efficiency calibration process and the coincidence summing corrections, appear jointly. The full-energy peak and the total efficiencies from the two methods typically agree with discrepancy 10%. The discrepancy between the simulation, ANGLE4 and measured full-energy peak after corrections for the coincidence summing effect was on the average, while not exceeding 14%. Therefore, this technique can be easily applied in establishing the efficiency calibration curves of well-type detectors.

Black Hole Accretion in Gamma Ray Bursts

We study the structure and evolution of the hyperaccreting disks and outflows in the gamma ray bursts central engines. The torus around a stellar mass black hole is composed of free nucleons, Helium, electron-positron pairs, and is cooled by neutrino emission. Accretion of matter powers the relativistic jets, responsible for the gamma ray prompt emission. The significant number density of neutrons in the disk and outflowing material will cause subsequent formation of heavier nuclei. We study the process of nucleosynthesis and its possible observational consequences. We also apply our scenario to the recent observation of the gravitational wave signal, detected on 14 September 2015 by the two Advanced LIGO detectors, and related to an inspiral and merger of a binary black hole system. A gamma ray burst that could possibly be related with the GW150914 event was observed by the Fermi satellite. It had a duration of about 1 s and appeared about 0.4 s after the gravitational-wave signal. We propose that a collapsing massive star and a black hole in a close binary could lead to the event. The gamma ray burst was powered by a weak neutrino flux produced in the star remnant’s matter. Low spin and kick velocity of the merged black hole are reproduced in our simulations. Coincident gravitational-wave emission originates from the merger of the collapsed core and the companion black hole.

The LPM effect in sequential bremsstrahlung: dimensional regularization

The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. Of recent interest is the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD). In previous papers, we have developed methods for computing such corrections without making soft-gluon approximations. However, our methods require consistent treatment of canceling ultraviolet (UV) divergences associated with coincident emission times, even for processes with tree-level amplitudes. In this paper, we show how to use dimensional regularization to properly handle the UV contributions. We also present a simple diagnostic test that any consistent UV regularization method for this problem needs to pass.

Search for transient gravitational waves in coincidence with short-duration radio transients during 2007–2013

We present an archival search for transient gravitational-wave bursts in coincidence with 27 single pulse triggers from Green Bank Telescope pulsar surveys, using the LIGO, Virgo and GEO interferometer network. We also discuss a check for gravitational-wave signals in coincidence with Parkes Fast Radio Bursts using similar methods. Data analyzed in these searches were collected between 2007 and 2013. Possible sources of emission of both short-duration radio signals and transient gravitational-wave emission include starquakes on neutron stars, binary coalescence of neutron stars, and cosmic string cusps. While no evidence for gravitational-wave emission in coincidence with these radio transients was found, the current analysis serves as a prototype for similar future searches using more sensitive second-generation interferometers.

Global air quality and climate

Emissions of air pollutants and their precursors determine regional air quality and can alter climate. Climate change can perturb the long-range transport, chemical processing, and local meteorology that influence air pollution. We review the implications of projected changes in methane (CH(4)), ozone precursors (O(3)), and aerosols for climate (expressed in terms of the radiative forcing metric or changes in global surface temperature) and hemispheric-to-continental scale air quality. Reducing the O(3) precursor CH(4) would slow near-term warming by decreasing both CH(4) and tropospheric O(3). Uncertainty remains as to the net climate forcing from anthropogenic nitrogen oxide (NO(x)) emissions, which increase tropospheric O(3) (warming) but also increase aerosols and decrease CH(4) (both cooling). Anthropogenic emissions of carbon monoxide (CO) and non-CH(4) volatile organic compounds (NMVOC) warm by increasing both O(3) and CH(4). Radiative impacts from secondary organic aerosols (SOA) are poorly understood. Black carbon emission controls, by reducing the absorption of sunlight in the atmosphere and on snow and ice, have the potential to slow near-term warming, but uncertainties in coincident emissions of reflective (cooling) aerosols and poorly constrained cloud indirect effects confound robust estimates of net climate impacts. Reducing sulfate and nitrate aerosols would improve air quality and lessen interference with the hydrologic cycle, but lead to warming. A holistic and balanced view is thus needed to assess how air pollution controls influence climate; a first step towards this goal involves estimating net climate impacts from individual emission sectors. Modeling and observational analyses suggest a warming climate degrades air quality (increasing surface O(3) and particulate matter) in many populated regions, including during pollution episodes. Prior Intergovernmental Panel on Climate Change (IPCC) scenarios (SRES) allowed unconstrained growth, whereas the Representative Concentration Pathway (RCP) scenarios assume uniformly an aggressive reduction, of air pollutant emissions. New estimates from the current generation of chemistry-climate models with RCP emissions thus project improved air quality over the next century relative to those using the IPCC SRES scenarios. These two sets of projections likely bracket possible futures. We find that uncertainty in emission-driven changes in air quality is generally greater than uncertainty in climate-driven changes. Confidence in air quality projections is limited by the reliability of anthropogenic emission trajectories and the uncertainties in regional climate responses, feedbacks with the terrestrial biosphere, and oxidation pathways affecting O(3) and SOA.

FERMILARGE AREA TELESCOPE OBSERVATIONS OF THE SUPERNOVA REMNANT G8.7–0.1

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) onboard the \emph{Fermi} Gamma-ray Space Telescope. An investigation of the relationship among G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially-connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV--100 GeV can be described by a broken power-law function with a break of 2.4 $\pm$ 0.6 (stat) $\pm$ 1.2 (sys) GeV, and photon indices of 2.10 $\pm$ 0.06 (stat) $\pm$ 0.10 (sys) below the break and 2.70 $\pm$ 0.12 (stat) $\pm$ 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7$-$0.1, and the molecular clouds, the decay of $\pi^{0}$s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804$-$216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7$-$0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

The Timing Counter of the MEG experiment: calibration and performance

The MEG detector is designed to test Lepton Flavor Violation in the $\mu^+\rightarrow e^+\gamma$ decay down to a Branching Ratio of a few $10^{-13}$. The decay topology consists in the coincident emission of a monochromatic photon in direction opposite to a monochromatic positron. A precise measurement of the relative time $t_{e^+\gamma}$ is crucial to suppress the background. The Timing Counter (TC) is designed to precisely measure the time of arrival of the $e^+$ and to provide information to the trigger system. It consists of two sectors up and down stream the decay target, each consisting of two layers. The outer one made of scintillating bars and the inner one of scintillating fibers. Their design criteria and performances are described.

Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory

The advent of the Auger Engineering Radio Array (AERA) necessitates the development of a powerful framework for the analysis of radio measurements of cosmic ray air showers. As AERA performs “radio-hybrid” measurements of air shower radio emission in coincidence with the surface particle detectors and fluorescence telescopes of the Pierre Auger Observatory, the radio analysis functionality had to be incorporated in the existing hybrid analysis solutions for fluorescence and surface detector data. This goal has been achieved in a natural way by extending the existing Auger Offline software framework with radio functionality. In this article, we lay out the design, highlights and features of the radio extension implemented in the Auger Offline framework. Its functionality has achieved a high degree of sophistication and offers advanced features such as vectorial reconstruction of the electric field, advanced signal processing algorithms, a transparent and efficient handling of FFTs, a very detailed simulation of detector effects, and the read-in of multiple data formats including data from various radio simulation codes. The source code of this radio functionality can be made available to interested parties on request.

K−absorption at rest in nuclei followed bypΛemission

$p\,\Lambda$ emission in coincidence following $K^-$ absorption at rest in nuclei is studied using quantum mechanical scattering theory and nuclear wave functions. $K^-$ absorption is assumed to occur on two protons in the nucleus. In the formalism, emphasis is put on the study of the final state interaction (FSI) effects of $p$ and $\Lambda$ with the recoiling nucleus. We include elastic scattering and single nucleon knock-out (KO) channels in the FSI. Calculations are presented for the $^{12}$C nucleus, using shell model wave functions, and without any extra mass modification of the $K^-\,pp$ system in the nucleus. Calculated results are presented for the angular correlation distribution between $p$ and $\Lambda$, their invariant mass distribution and the momentum spectra of $p$ and $\Lambda$. These results are compared with the corresponding experimental measurements \cite{agnello}. With only elastic scattering FSI included, the angular correlation distribution and the momentum spectra are found to be in good accord with the corresponding measurements. With full FSI the calculated $p\,\Lambda$ invariant mass distribution is found to have two peaks, one corresponding to the elastic scattering FSI and another to single nucleon KO FSI. The KO peak agrees fully, in position and shape, with the peak observed in Ref. \cite{agnello}. The peak corresponding to elastic scattering FSI does not seem to exist in the measured distribution. Considering that such a two peak structure is always seen in the inclusive ($p$, $p^\prime $) and ($e$, $e^\prime $) reactions in nuclei at intermediate energies, absence of the elastic scattering peak in the $p\,\Lambda$ reaction is intriguing.