The Experts below are selected from a list of 11469 Experts worldwide ranked by ideXlab platform
J F Ormes - One of the best experts on this subject based on the ideXlab platform.
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propagation of secondary Antiprotons and cosmic rays in the galaxy
Advances in Space Research, 2005Co-Authors: I V Moskalenko, J F Ormes, A W Strong, S G MashnikAbstract:Recent more accurate antiproton data obtained by the BESS team during the last solar minimum pose a challenge to conventional propagation models of cosmic rays. In particular, the diffusive reacceleration model, which matches well key secondary/primary isotope ratios in cosmic rays, fails to reproduce the secondary antiproton spectrum. Tuning both secondary/primary isotope ratios and Antiprotons is possible, but requires artificial breaks in the diffusion coefficient and the injection spectrum of primaries. We will discuss some possibilities to overcome these difficulties in the propagation models. We will present new results of our calculation of CR propagation in the Galaxy using the GALPROP code.
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secondary Antiprotons and propagation of cosmic rays in the galaxy and heliosphere
The Astrophysical Journal, 2002Co-Authors: I V Moskalenko, J F Ormes, A W Strong, M S PotgieterAbstract:High-energy collisions of cosmic-ray nuclei with interstellar gas are believed to be the mechanism producing the majority of cosmic-ray Antiprotons. Because of the kinematics of the process, they are created with a nonzero momentum; the characteristic spectral shape with a maximum at D2 GeV and a sharp decrease toward lower energies makes Antiprotons a unique probe of models for particle propagation in the Galaxy and modulation in the heliosphere. On the other hand, accurate calculation of the secondary antiproton —ux provides a ii background ˇˇ for searches for exotic signals from the annihilation of supersymmetric particles and primordial black hole evaporation. Recently, new data with large statistics on both low- and high-energy antiproton —uxes have become available which allow such tests to be performed. We use our propagation code GALPROP to calculate interstellar cosmic-ray propagation for a variety of models. We show that there is no simple model capable of accurately describing the whole variety of data: boron/carbon and sub-iron/iron ratios, spectra of protons, helium, Antiprotons, positrons, electrons, and diUuse c-rays. We —nd that only a model with a break in the diUusion coefficient plus convection can reproduce measurements of cosmic-ray species, and the reproduction of primaries (p, He) can be further improved by introducing a break in the primary injection spectra. For our best-—t model we make predictions of proton and antiproton —uxes near the Earth for diUerent modulation levels and magnetic polarity using a steady state drift model of propagation in the heliosphere.
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secondary Antiprotons and propagation of cosmic rays in the galaxy and heliosphere
arXiv: Astrophysics, 2001Co-Authors: I V Moskalenko, J F Ormes, A W Strong, M S PotgieterAbstract:High-energy collisions of cosmic-ray nuclei with interstellar gas are believed to be the mechanism producing the majority of cosmic ray Antiprotons. Due to the kinematics of the process they are created with a nonzero momentum; the characteristic spectral shape with a maximum at ~2 GeV and a sharp decrease towards lower energies makes Antiprotons a unique probe of models for particle propagation in the Galaxy and modulation in the heliosphere. On the other hand, accurate calculation of the secondary antiproton flux provides a ``background'' for searches for exotic signals from the annihilation of supersymmetric particles and primordial black hole evaporation. Recently new data with large statistics on both low and high energy antiproton fluxes have become available which allow such tests to be performed. We use our propagation code GALPROP to calculate interstellar cosmic-ray propagation for a variety of models. We show that there is no simple model capable of accurately describing the whole variety of data: boron/carbon and sub-iron/iron ratios, spectra of protons, helium, Antiprotons, positrons, electrons, and diffuse gamma rays. We find that only a model with a break in the diffusion coefficient plus convection can reproduce measurements of cosmic-ray species, and the reproduction of primaries (p, He) can be further improved by introducing a break in the primary injection spectra. For our best-fit model we make predictions of proton and antiproton fluxes near the Earth for different modulation levels and magnetic polarity using a steady-state drift model of propagation in the heliosphere.
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secondary Antiprotons in cosmic rays
arXiv: Astrophysics, 2001Co-Authors: I V Moskalenko, J F Ormes, A W Strong, M S Potgieter, U W LangnerAbstract:High energy collisions of cosmic ray (CR) nuclei with interstellar gas are believed to be the mechanism producing the majority of CR Antiprotons. The distinguishing spectral shape with a maximum at 2 GeV and a sharp decrease towards lower energies makes Antiprotons a unique probe of the models of particle propagation in the Galaxy and modulation in the heliosphere. Besides, accurate calculation of the secondary antiproton flux provides a ``background'' for searches for exotic signals from the annihilation of supersymmetric particles and primordial black hole evaporation. Recently new data with large statistics on the antiproton flux have become available which allow for such tests to be performed. We use our 3D Galactic cosmic ray propagation code GALPROP to calculate interstellar propagation in several models. For our best model we make predictions of proton and antiproton fluxes near the Earth for different modulation levels and polarity using a steady-state drift model for heliospheric modulation.
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Antiprotons below 200 mev in the interstellar medium perspectives for observing exotic matter signatures
arXiv: Astrophysics, 2001Co-Authors: I V Moskalenko, E R Christian, A A Moiseev, J F Ormes, A W StrongAbstract:Most cosmic ray Antiprotons observed near the Earth are secondaries produced in collisions of energetic cosmic ray (CR) particles with interstellar gas. The spectrum of secondary Antiprotons is expected to peak at ~2 GeV and decrease sharply at lower energies. This leaves a low energy window in which to look for signatures of exotic processes such as evaporation of primordial black holes or dark matter annihilation. In the inner heliosphere, however, modulation of CRs by the solar wind makes analysis difficult. Detecting these Antiprotons outside the heliosphere on an interstellar probe removes most of the complications of modulation. We present a new calculation of the expected secondary antiproton flux (the background) as well as a preliminary design of a light-weight, low-power instrument for the interstellar probe to make such measurements.
I V Moskalenko - One of the best experts on this subject based on the ideXlab platform.
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new calculation of antiproton production by cosmic ray protons and nuclei
The Astrophysical Journal, 2015Co-Authors: M Kachelriess, I V Moskalenko, S OstapchenkoAbstract:A dramatic increase in the accuracy and statistics of space-borne cosmic ray (CR) measurements has yielded several breakthroughs over the last several years. The most puzzling is the rise in the positron fraction above ∼10 GeV over the predictions of the propagation models assuming pure secondary production. The accuracy of the antiproton production cross section is critical for a strophysical applications and searches for new physics since Antiprotons in CRs seem to hold the keys to many puzzles including the origin of those excess positrons. However, model calculations of antiproton production in CR interactions with interstellar gas are often employing parameterizations that are out of date or are using outdated physical concepts. That may lead to an incorrect interpretation of antiproton data which could have broad consequences for other areas of astrophysics. In this work, we calculate antiproton production in pp-, pA-, and AA-interactions using EPOS-LHC and QGSJET-II04, two of the most advanced Monte Carlo (MC) generators tuned to numerous accelerator data including those from the Large Hadron Collider (LHC). We show that the antiproton yields obtained with these MC generators differ by up to an order of magnitude from yields of parameterizations commonly used in astrophysics.
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propagation of secondary Antiprotons and cosmic rays in the galaxy
Advances in Space Research, 2005Co-Authors: I V Moskalenko, J F Ormes, A W Strong, S G MashnikAbstract:Recent more accurate antiproton data obtained by the BESS team during the last solar minimum pose a challenge to conventional propagation models of cosmic rays. In particular, the diffusive reacceleration model, which matches well key secondary/primary isotope ratios in cosmic rays, fails to reproduce the secondary antiproton spectrum. Tuning both secondary/primary isotope ratios and Antiprotons is possible, but requires artificial breaks in the diffusion coefficient and the injection spectrum of primaries. We will discuss some possibilities to overcome these difficulties in the propagation models. We will present new results of our calculation of CR propagation in the Galaxy using the GALPROP code.
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secondary Antiprotons and propagation of cosmic rays in the galaxy and heliosphere
The Astrophysical Journal, 2002Co-Authors: I V Moskalenko, J F Ormes, A W Strong, M S PotgieterAbstract:High-energy collisions of cosmic-ray nuclei with interstellar gas are believed to be the mechanism producing the majority of cosmic-ray Antiprotons. Because of the kinematics of the process, they are created with a nonzero momentum; the characteristic spectral shape with a maximum at D2 GeV and a sharp decrease toward lower energies makes Antiprotons a unique probe of models for particle propagation in the Galaxy and modulation in the heliosphere. On the other hand, accurate calculation of the secondary antiproton —ux provides a ii background ˇˇ for searches for exotic signals from the annihilation of supersymmetric particles and primordial black hole evaporation. Recently, new data with large statistics on both low- and high-energy antiproton —uxes have become available which allow such tests to be performed. We use our propagation code GALPROP to calculate interstellar cosmic-ray propagation for a variety of models. We show that there is no simple model capable of accurately describing the whole variety of data: boron/carbon and sub-iron/iron ratios, spectra of protons, helium, Antiprotons, positrons, electrons, and diUuse c-rays. We —nd that only a model with a break in the diUusion coefficient plus convection can reproduce measurements of cosmic-ray species, and the reproduction of primaries (p, He) can be further improved by introducing a break in the primary injection spectra. For our best-—t model we make predictions of proton and antiproton —uxes near the Earth for diUerent modulation levels and magnetic polarity using a steady state drift model of propagation in the heliosphere.
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secondary Antiprotons and propagation of cosmic rays in the galaxy and heliosphere
arXiv: Astrophysics, 2001Co-Authors: I V Moskalenko, J F Ormes, A W Strong, M S PotgieterAbstract:High-energy collisions of cosmic-ray nuclei with interstellar gas are believed to be the mechanism producing the majority of cosmic ray Antiprotons. Due to the kinematics of the process they are created with a nonzero momentum; the characteristic spectral shape with a maximum at ~2 GeV and a sharp decrease towards lower energies makes Antiprotons a unique probe of models for particle propagation in the Galaxy and modulation in the heliosphere. On the other hand, accurate calculation of the secondary antiproton flux provides a ``background'' for searches for exotic signals from the annihilation of supersymmetric particles and primordial black hole evaporation. Recently new data with large statistics on both low and high energy antiproton fluxes have become available which allow such tests to be performed. We use our propagation code GALPROP to calculate interstellar cosmic-ray propagation for a variety of models. We show that there is no simple model capable of accurately describing the whole variety of data: boron/carbon and sub-iron/iron ratios, spectra of protons, helium, Antiprotons, positrons, electrons, and diffuse gamma rays. We find that only a model with a break in the diffusion coefficient plus convection can reproduce measurements of cosmic-ray species, and the reproduction of primaries (p, He) can be further improved by introducing a break in the primary injection spectra. For our best-fit model we make predictions of proton and antiproton fluxes near the Earth for different modulation levels and magnetic polarity using a steady-state drift model of propagation in the heliosphere.
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secondary Antiprotons in cosmic rays
arXiv: Astrophysics, 2001Co-Authors: I V Moskalenko, J F Ormes, A W Strong, M S Potgieter, U W LangnerAbstract:High energy collisions of cosmic ray (CR) nuclei with interstellar gas are believed to be the mechanism producing the majority of CR Antiprotons. The distinguishing spectral shape with a maximum at 2 GeV and a sharp decrease towards lower energies makes Antiprotons a unique probe of the models of particle propagation in the Galaxy and modulation in the heliosphere. Besides, accurate calculation of the secondary antiproton flux provides a ``background'' for searches for exotic signals from the annihilation of supersymmetric particles and primordial black hole evaporation. Recently new data with large statistics on the antiproton flux have become available which allow for such tests to be performed. We use our 3D Galactic cosmic ray propagation code GALPROP to calculate interstellar propagation in several models. For our best model we make predictions of proton and antiproton fluxes near the Earth for different modulation levels and polarity using a steady-state drift model for heliospheric modulation.
Y Yamazaki - One of the best experts on this subject based on the ideXlab platform.
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the asacusa micromegas tracker a cylindrical bulk micromegas detector for antimatter research
Review of Scientific Instruments, 2015Co-Authors: B Radics, N Kuroda, Y Nagata, Y Yamazaki, S Ishikawa, Y Matsuda, M Anfreville, S Aune, M Boyer, F ChateauAbstract:The ASACUSA Micromegas Tracker (AMT; ASACUSA: Atomic Spectroscopy and Collisions Using Slow Antiprotons) was designed to be able to reconstruct antiproton-nucleon annihilation vertices in three dimensions. The goal of this device is to study antihydrogen formation processes in the ASACUSA cusp trap, which was designed to synthesise a spin-polarised antihydrogen beam for precise tests of Charge, Parity, and Time (CPT) symmetry invariance. This paper discusses the structure and technical details of an AMT detector built into such an environment, its data acquisition system and the first performance with cosmic rays.
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atomic collision and spectroscopy experiments with ultra low energy Antiprotons
Journal of Physics: Conference Series, 2009Co-Authors: Hiroyuki A Torii, N Kuroda, H Imao, Y Nagata, V L Varentsov, Hiroshi Toyoda, Y YamazakiAbstract:Antiproton, the antiparticle of proton, is a unique projectile in the study of atomic collision physics, which can be treated theoretically either as a 'negative proton' or a 'heavy electron'. Atomic capture of an antiproton will result in formation of a highly excited exotic atom. Antiprotonic helium atom has been studied intensively by means of precision laser spectroscopy, which has led to a stringent determination of antiproton mass and charge to a level of ppb. Comparison of these values with those of proton gives one of the best tests of CPT invariance, the most fundamental symmetry in physics. However, the dynamic processes of antiproton capture remain unclarified. With an aim to produce an antiproton beam at atomic-physics energies for 'pure' collision experiments, we have so far developed techniques to decelerate, cool and confine Antiprotons in vacuo, using a sequential combination of the Antiproton Decelerator (AD) at CERN, a Radio-Frequency Quadrupole Decelerator (RFQD), and an electromagnetic trap. Our recent success in stable extraction of monoenergetic ultra-slow Antiprotons, about 3 × 10 5 in number available every 5 minutes, has opened up the possibility to study ionization and atomic capture processes between an antiproton and an atom under the single collision condition. Our design and strategy of the cross-beam experiments are presented, together with technical challenges in the detection system to identify the rare events with a reaction rate of 10 −4 .
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cross beam atomic collision experiment between ultra low energy Antiprotons and a supersonic gas jet
Hyperfine Interactions, 2009Co-Authors: Hiroyuki A Torii, N Kuroda, H Imao, Y Nagata, V L Varentsov, Hiroshi Toyoda, Y YamazakiAbstract:The antiproton is a unique projectile in the study of atomic collision physics. With an aim to produce an antiproton beam at atomic-physics energies for ‘pure’ collision experiments, we have so far developed techniques to decelerate, cool and confine Antiprotons in vacuo. Our recent success in stable extraction of the beam has opened up the possibility to study ionization and atomic capture processes between an antiproton and an atom at an unprecedented low energy from 10 eV to 1 keV under the single-collision condition. We have prepared a powerful supersonic helium gas jet to be crossed with the antiproton beam. The reaction rate is of the order of 10 − 4, and rigorous identification of particles is required for reduction of huge background counts. The reaction events are recognized by an electron signal followed by antiproton annihilation with an appropriate interval in the time of flight. Our design and strategy of the experiment are presented.
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observation of ultra slow Antiprotons using micro channel plate
PROCEEDINGS OF THE WORKSHOP ON COLD ANTIMATTER PLASMAS AND APPLICATION TO#N#FUNDAMENTAL PHYSICS, 2008Co-Authors: H Imao, H A Torii, Y Nagata, Y Kanai, A Mohri, Hiroshi Toyoda, H Higaki, T Shimoyama, Y Enomoto, Y YamazakiAbstract:Our group ASACUSA‐MUSASHI has succeeded in accumulating several million Antiprotons and extracting them as monochromatic ultra‐slow antiproton beams (10 eV–1 keV) at CERN AD. We have observed ultra‐slow Antiprotons using micro‐channel plates (MCP). The integrated pulse area of the output signals generated when the MCP was irradiated by ultra‐slow Antiprotons was 6 times higher than that by electrons. As a long‐term effect, we also observed an increase in the background rate presumably due to the radioactivation of the MCP surface. Irradiating the antiproton beams on the MCP induces antiproton‐nuclear annihilations only on the first layer of the surface. Low‐energy and short‐range secondary particles like charged nuclear fragments caused by the “surface nuclear reactions” would be the origin of our observed phenomena.
James D Wells - One of the best experts on this subject based on the ideXlab platform.
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illuminating dark matter and primordial black holes with interstellar Antiprotons
The Astrophysical Journal, 1999Co-Authors: J F Ormes, Alexander Moiseev, James D WellsAbstract:Interstellar antiproton fluxes can arise from dark matter annihilating or decaying into quarks or gluons that subsequently fragment into Antiprotons. Evaporation of primordial black holes can also produce a significant antiproton cosmic-ray flux. Since the background of secondary Antiprotons from spallation has an interstellar energy spectrum that peaks at ~2 GeV and falls rapidly for energies below this, low-energy measurements of cosmic Antiprotons are useful in the search for exotic antiproton sources. However, measurement of the flux near the Earth is challenged by significant uncertainties arising from the effects of the solar wind. We suggest evading this problem and more effectively probing dark matter signals by placing an antiproton spectrometer aboard an interstellar probe currently under discussion. We address the experimental challenges of a light, low-power-consuming detector, and present an initial design of such an instrument. This experimental effort could significantly increase our ability to detect, and have confidence in, a signal from exotic, nonstandard antiproton sources. Furthermore, solar modulation effects in the heliosphere could be better quantified and understood by comparing results to inverse modulated data derived from existing balloon and space-based detectors near the Earth.
Y Nagata - One of the best experts on this subject based on the ideXlab platform.
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imaging antimatter with a micromegas detector
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2018Co-Authors: V Mackel, P. Dupre, N Kuroda, Y Nagata, Y Kanai, B Radics, Y Matsuda, H Higaki, M Tajima, E WidmannAbstract:Abstract The ASACUSA collaboration aims at measuring the ground state hyperfine splitting of antihydrogen for probing fundamental symmetries. A cryogenic trap for mixing Antiprotons and positrons serves as an antihydrogen source for in-flight spectroscopy. In order to be able to monitor the antihydrogen formation process, a dedicated Micromegas tracking detector has been designed and built to record the annihilation distribution in the trap. In this paper, we present the first results from antiproton annihilation data recorded with the Micromegas, together with a description of the event reconstruction algorithm.
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the asacusa micromegas tracker a cylindrical bulk micromegas detector for antimatter research
Review of Scientific Instruments, 2015Co-Authors: B Radics, N Kuroda, Y Nagata, Y Yamazaki, S Ishikawa, Y Matsuda, M Anfreville, S Aune, M Boyer, F ChateauAbstract:The ASACUSA Micromegas Tracker (AMT; ASACUSA: Atomic Spectroscopy and Collisions Using Slow Antiprotons) was designed to be able to reconstruct antiproton-nucleon annihilation vertices in three dimensions. The goal of this device is to study antihydrogen formation processes in the ASACUSA cusp trap, which was designed to synthesise a spin-polarised antihydrogen beam for precise tests of Charge, Parity, and Time (CPT) symmetry invariance. This paper discusses the structure and technical details of an AMT detector built into such an environment, its data acquisition system and the first performance with cosmic rays.
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atomic collision and spectroscopy experiments with ultra low energy Antiprotons
Journal of Physics: Conference Series, 2009Co-Authors: Hiroyuki A Torii, N Kuroda, H Imao, Y Nagata, V L Varentsov, Hiroshi Toyoda, Y YamazakiAbstract:Antiproton, the antiparticle of proton, is a unique projectile in the study of atomic collision physics, which can be treated theoretically either as a 'negative proton' or a 'heavy electron'. Atomic capture of an antiproton will result in formation of a highly excited exotic atom. Antiprotonic helium atom has been studied intensively by means of precision laser spectroscopy, which has led to a stringent determination of antiproton mass and charge to a level of ppb. Comparison of these values with those of proton gives one of the best tests of CPT invariance, the most fundamental symmetry in physics. However, the dynamic processes of antiproton capture remain unclarified. With an aim to produce an antiproton beam at atomic-physics energies for 'pure' collision experiments, we have so far developed techniques to decelerate, cool and confine Antiprotons in vacuo, using a sequential combination of the Antiproton Decelerator (AD) at CERN, a Radio-Frequency Quadrupole Decelerator (RFQD), and an electromagnetic trap. Our recent success in stable extraction of monoenergetic ultra-slow Antiprotons, about 3 × 10 5 in number available every 5 minutes, has opened up the possibility to study ionization and atomic capture processes between an antiproton and an atom under the single collision condition. Our design and strategy of the cross-beam experiments are presented, together with technical challenges in the detection system to identify the rare events with a reaction rate of 10 −4 .
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cross beam atomic collision experiment between ultra low energy Antiprotons and a supersonic gas jet
Hyperfine Interactions, 2009Co-Authors: Hiroyuki A Torii, N Kuroda, H Imao, Y Nagata, V L Varentsov, Hiroshi Toyoda, Y YamazakiAbstract:The antiproton is a unique projectile in the study of atomic collision physics. With an aim to produce an antiproton beam at atomic-physics energies for ‘pure’ collision experiments, we have so far developed techniques to decelerate, cool and confine Antiprotons in vacuo. Our recent success in stable extraction of the beam has opened up the possibility to study ionization and atomic capture processes between an antiproton and an atom at an unprecedented low energy from 10 eV to 1 keV under the single-collision condition. We have prepared a powerful supersonic helium gas jet to be crossed with the antiproton beam. The reaction rate is of the order of 10 − 4, and rigorous identification of particles is required for reduction of huge background counts. The reaction events are recognized by an electron signal followed by antiproton annihilation with an appropriate interval in the time of flight. Our design and strategy of the experiment are presented.
-
observation of ultra slow Antiprotons using micro channel plate
PROCEEDINGS OF THE WORKSHOP ON COLD ANTIMATTER PLASMAS AND APPLICATION TO#N#FUNDAMENTAL PHYSICS, 2008Co-Authors: H Imao, H A Torii, Y Nagata, Y Kanai, A Mohri, Hiroshi Toyoda, H Higaki, T Shimoyama, Y Enomoto, Y YamazakiAbstract:Our group ASACUSA‐MUSASHI has succeeded in accumulating several million Antiprotons and extracting them as monochromatic ultra‐slow antiproton beams (10 eV–1 keV) at CERN AD. We have observed ultra‐slow Antiprotons using micro‐channel plates (MCP). The integrated pulse area of the output signals generated when the MCP was irradiated by ultra‐slow Antiprotons was 6 times higher than that by electrons. As a long‐term effect, we also observed an increase in the background rate presumably due to the radioactivation of the MCP surface. Irradiating the antiproton beams on the MCP induces antiproton‐nuclear annihilations only on the first layer of the surface. Low‐energy and short‐range secondary particles like charged nuclear fragments caused by the “surface nuclear reactions” would be the origin of our observed phenomena.