Data from the Payload for Antimatter Matter Exploration and Light‐nuclei Astrophysics (PAMELA) satellite experiment were used to measure the geomagnetic cutoff for high‐energy (≳ 80MeV) protons ...during the 14 December 2006 geomagnetic storm. The variations of the cutoff latitude as a function of rigidity were studied on relatively short timescales, corresponding to spacecraft orbital periods (∼94 min). Estimated cutoff values were compared with those obtained by means of a trajectory‐tracing approach based on a dynamical empirical modeling of the Earth's magnetosphere. We found significant variations in the cutoff latitude, with a maximum suppression of ∼7° at lowest rigidities during the main phase of the storm. The observed reduction in the geomagnetic shielding and its temporal evolution were related to the changes in the magnetospheric configuration, investigating the role of interplanetary magnetic field, solar wind, and geomagnetic parameters. PAMELA's results represent the first direct measurement of geomagnetic cutoffs for protons with kinetic energies in the sub‐GeV and GeV region.
Key Points
Direct measurement of high‐energy proton cutoffs during the 14 December 2006 magnetospheric storm
Significant reduction in the geomagnetic shielding observed, with a 7 degree maximum suppression
Cutoff changes well correlated with the IMF strength, its Z component, SYM‐H, and, especially, Kp
We present a precise measurement of the ratio RK=Γ(K→eν(γ))/Γ(K→μν(γ)) and a study of the radiative process K→eνγ, performed with the KLOE detector. The results are based on data collected at the ...Frascati e+e− collider DAΦNE for an integrated luminosity of 2.2 fb−1. We find RK=(2.493±0.025stat±0.019syst)×10−5, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation. We also measured the differential decay rate dΓ(K→eνγ)/dEγ for photon energies 10<Eγ< 250 MeV. Results are compared with predictions from theory.
We report an accurate measurement of the geomagnetically trapped proton fluxes for kinetic energy above ~70 MeV performed by the PAMELA mission at low Earth orbits (350 / 610 km). Data were analyzed ...in the frame of the adiabatic theory of charged particle motion in the geomagnetic field. Flux properties were investigated in detail, providing a full characterization of the particle radiation in the South Atlantic Anomaly region, including locations, energy spectra, and pitch angle distributions. PAMELA results significantly improve the description of the Earth's radiation environment at low altitudes, placing important constraints on the trapping and interaction processes, and can be used to validate current trapped particle radiation models.
The PAMELA space experiment is providing first direct observations of Solar Energetic Particles (SEPs) with energies from about 80 MeV to several GeV in near-Earth orbit, bridging the low energy ...measurements by other spacecrafts and the Ground Level Enhancement (GLE) data by the worldwide network of neutron monitors. Its unique observational capabilities include the possibility of measuring the flux angular distribution and thus investigating possible anisotropies associated to SEP events. The analysis is supported by an accurate back-tracing simulation based on a realistic description of the Earth's magnetosphere, which is exploited to estimate the SEP energy spectra as a function of the asymptotic direction of arrival with respect to the Interplanetary Magnetic Field (IMF). In this work we report the results for the May 17, 2012 event.
We present here the development of resistive Micromegas with O(mm 2 ) pad readout aiming at improving the high rate capability of the detector. The goal application is precision tracking in high rate ...environment without efficiency loss up to few MHz/cm 2 . In the proposed layout, small anode pads are overlayed by an insulating layer with a pattern of resistive pads on top. The readout and resistive pads are connected by intermediate resistors embedded in the insulating layer. A first prototype has been constructed at CERN and thoroughly tested. It consists of a 48x16 matrix of 0.8x2.8 mm 2 rectangular pads with a pitch of 1 and 3 mm in the two coordinates. The active surface is 4.8x4.8 cm 2 with a total number of 768 channels read-out by 6 APV-25 chips. The drift and amplification gaps of this Micromegas prototype are 5 mm and 128 \mu \mathrm{m}, respectively. The detector is operated with an Ar/CO2 (93:7) gas mixture. Characterization and performance studies of the detector have been carried out by means of radioactive sources, X-Rays and test beam.
The PAMELA detector was launched on June 15th of 2006 on board the Russian Resurs-DK1 satellite and during ten years of continuous data-taking it has observed very interesting features in cosmic ...rays, especially in the fluxes of protons, helium and electrons. Moreover, PAMELA measurements of cosmic antiproton and positron fluxes and positron-to-all-electron ratio have set strong constraints to the nature of Dark Matter. Measurements of boron, carbon, lithium and beryllium (together with the isotopic fraction) have also shed new light on the elemental composition of the cosmic radiation. Search for signatures of more exotic processes (such as the ones involving Strange Quark Matter) has also been pursued. Furthermore, over the years the instrument has allowed a constant monitoring of the solar activity and a prolonged study of the solar modulation, improving the comprehension of the heliosphere mechanisms. PAMELA has also measured the radiation environment around the Earth, and detected for the first time the presence of an antiproton radiation belt surrounding our planet. In this highlight paper PAMELA main results will be reviewed.
Motivated mainly by future upgrades at high-luminosity LHC (HL-LHC) and detectors at future accelerators, most of the HEP R&D collaborations are focusing on the design of new particle detectors for ...operation under high particle flow. In the field of Micro-Pattern-Gaseous-Detectors, were designed the small-pad resistive Micromegas prototypes, to overcome the limitations of current resistive strip Micromegas chambers. In these new prototypes, pads with 1×3 mm 2 area replace the readout strips to reduce the occupancy. The spark protection resistive layer has been redesigned and optimized with different techniques to permit a safe behavior of the detector, at rates of the order of tens MHz/cm 2 over large surfaces without efficiency loss. The firstly-developed design exploits a pad-patterned embedded resistor layout made by screen-printing, while the most recent technique involves uniform sputtered DLC (Diamond Like Carbon structure) layers, where the charge evacuates through the several vias connected to the ground. Comparative studies have been conducted on the performance of the detectors with two resistive layouts, and between two DLC prototypes with different pitch of vias and surface resistivity. The results of the tests performed with high intensity X-rays and with high-energy charged particle beams will be presented.
We present a new limit on the production of a light dark-force mediator with the KLOE detector at DAΦNE. This boson, called U, has been searched for in the decay ϕ→ηU, U→e+e−, analyzing the decay ...η→π0π0π0 in a data sample of 1.7 fb−1. No structures are observed in the e+e− invariant mass distribution over the background. This search is combined with a previous result obtained from the decay η→π+π−π0, increasing the sensitivity. We set an upper limit at 90% C.L. on the ratio between the U boson coupling constant and the fine structure constant of α′/α<1.7×10−5 for 30<MU<400 MeV and α′/α⩽8×10−6 for the sub-region 50<MU<210 MeV. This result assumes the Vector Meson Dominance expectations for the ϕηγ⁎ transition form factor. The dependence of this limit on the transition form factor has also been studied.
The satellite-borne PAMELA experiment has been continuously collecting data since 15th June 2006, when it was launched from the Baikonur cosmodrome to detect the charged component of cosmic rays over ...a wide energy range and with unprecedented statistics. The apparatus design is particularly suited for particle and antiparticle identification. The PAMELA experiment has measured the electron spectrum at Earth in great detail, extending up to about 100 GeV and down to about 200 MeV. The galactic cosmic ray electron spectra for 2007 and 2009, i.e. measured during the A<0 solar minimum of solar cycle 23, are presented. These fluxes provide important information for the study of charge dependent solar modulation effects.
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