32196561
Fermi Large 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) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between 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 ± 0.6 (stat) ± 1.2 (sys) GeV, and photon indices of 2.10 ± 0.06 (stat) ± 0.10 (sys) below the break and 2.70 ± 0.12 (stat) ± 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 π0s 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.
118693667
Gamma ray observations of the orion molecular clouds with the fermi large area telescope
We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between ∼100 MeV and ∼100 GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to ∼10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity-integrated CO intensity (WCO) at a 1◦ × 1◦ pixel level. The correlation is found to be linear over a WCO range of ∼10-fold when divided in three regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The WCO-to-mass conversion factor, XCO, is found to be ∼2.3 × 1020 cm−2 (K km s−1)−1 for the high-longitude part of Orion A (l > 212◦), ∼1.7 times higher than ∼1.3 × 1020 found for the rest of Orion A and B. We interpret the apparent high XCO in the high-longitude region of Orion A in the light of recent works proposing a nonlinear relation between H2 and CO densities in the diffuse molecular gas. WCO decreases faster than the H2 column density in the region making the gas "darker" to WCO.
55341209
OPERATION OF PEP IN A LOW EMITTANCE MODE
I’KI’ has I)crn IISC~ as a. source of synchrol.ron ra.diat.ion with at, 11nd~lat0r beam line operating parasitically tlurirtg particle pllysics runs at 14.5 GeV bca.m energy. ‘I’hc l)ossibi!ltlF. of using PEP in a dcdicntcrl mode for synchr0(1.011 racllat,lon have tenon considered. Since a lower bran1 r~~crgy is preferred in this cast, PEP has hcen succrssfully op~~ratctt at. 8 GeV where I.hr uricc,nplctl l~ra111 ctnittance is 27 null ratl. It is of int.erest to r~lucc this clnit.tance fnrther wit.h a tliffrrent opt,ics ha.ving strongrr horizont~al focnssing. This has I)een (lone by increasing tile horizontal heMron phase aclvauw per cell from 56” 1.0 I 00” resuIt.ing in an cmit,t,ance of about 9 1llJ1 rnd. To keep t,he strc~ngth of the sext 11p0lcs and their crV a l>eam was successfully injected and n.ccn~iiula.led. ‘I’he hol.izontal arid ~.~rtit.nl eniit tanccs were n~easllrc~tl Itsing the photon J)talll of the 58 111 long un(lulator hnnl lint- iI found to be 12.1 ant1 1 2 nnl ~,ntl. This is close to t,hr exp~ct,r~l value of 9.9 11111 ract for the SI~III of the two. The I)ealll lift, t.imr was over 30 110111.S at low cllrrcnts. Diffrrcn! mcltiods of rctliicing this emit.tancr cvcn further are invcst.iRat,e(l. Jncrcasillg tllc horizonl.al tlalnping pal.tition front .J, = rto .r, = 2 looks nlost prornisil.~g. This does uot rquirc new hardware bnl can IJ~ achieved WIllI a. s111nt1 increase of the RF-frequency of about ‘I kHz. Such au operation mode has been co~nputed ant1 tracked. The dyna.mic accrpt.ancr is very large and the expectrtl nnc~onplcd eniitt.ance is ,I.3 *11n rad at 8 (;eV.
119304648
RADIO AND γ-RAY CONSTRAINTS ON THE EMISSION GEOMETRY AND BIRTHPLACE OF PSR J2043+2740
We report on the first year of Fermi gamma-ray observations of pulsed high-energy emission from the old PSR J2043+2740. The study of the gamma-ray efficiency of such old pulsars gives us an insight into the evolution of pulsars' ability to emit in gammma rays as they age. The gamma-ray lightcurve of this pulsar above 0.1 GeV is clearly defined by two sharp peaks, 0.353+/-0.035 periods apart. We have combined the gamma-ray profile characteristics of PSR J2043+2740 with the geometrical properties of the pulsar's radio emission, derived from radio polarization data, and constrained the pulsar-beam geometry in the framework of a Two Pole Caustic and an Outer Gap model. The ranges of magnetic inclination and viewing angle were determined to be {alpha,zeta}~{52-57,61-68} for the Two Pole Caustic model, and {alpha,zeta}~{62-73,74-81} and {alpha,zeta}~{72-83,60-75} for the Outer Gap model. Based on this geometry, we assess possible birth locations for this pulsar and derive a likely proper motion, sufficiently high to be measurable with VLBI. At a characteristic age of 1.2 Myr, PSR J2043+2740 is the third oldest of all discovered, non-recycled, gamma-ray pulsars: it is twice as old as the next oldest, PSR J0357+32, and younger only than the recently discovered PSR J1836+5925 and PSR J2055+25, both of which are at least 5 and 10 times less energetic, respectively.
118924226
Analysis Methods for Milky Way Dark Matter Satellite Detection
The Gamma Ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) Dark Matter and New Physics Working group has been developing approaches for the indirect detection of in situ annihilation of dark matter. Our work has assumed that a significant component of dark matter is a new type of Weakly Interacting Massive Particle (WIMP) in the 100GeV mass range. The annihilation of two WIMPs results in the production of a large number of high energy gamma rays (>1GeV) that can be well measured by the GLAST LAT. The cold dark matter model implies a significant number of as yet unobserved dark matter satellites in our galaxy. The spectra of these galactic satellites are considerably harder than most, if not all, astrophysical sources, have an endpoint at the mass of the WIMP, and are not power laws. We describe a preliminary feasibility study for the indirect detection of dark matter satellites in the Milky Way using the GLAST LAT.
47886823
Fermi-LAT Study of Gamma-ray Emission in the Direction of Supernova Remnant W49B
We present an analysis of the gamma-ray data obtained with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the direction of SNR W49B (G43.3-0.2). A bright unresolved gamma-ray source detected at a significance of 38 sigma is found to coincide with SNR W49B. The energy spectrum in the 0.2-200 GeV range gradually steepens toward high energies. The luminosity is estimated to be 1.5x10^{36} (D/8 kpc)^2 erg s^-1 in this energy range. There is no indication that the gamma-ray emission comes from a pulsar. Assuming that the SNR shell is the site of gamma-ray production, the observed spectrum can be explained either by the decay of neutral pi mesons produced through the proton-proton collisions or by electron bremsstrahlung. The calculated energy density of relativistic particles responsible for the LAT flux is estimated to be remarkably large, U_{e,p}>10^4 eV cm^-3, for either gamma-ray production mechanism.
209835620
High-statistics study of neutral-pion pair production in two-photon collisions
The differential cross sections for the process gamma gamma -> pi(0)pi(0) have been measured in the kinematic range 0.6 GeV < W < 4.1 GeV, vertical bar cos theta* vertical bar < 0.8 in energy and pion scattering angle, respectively, in the gamma gamma center-of-mass system. The results are based on a 223 fb(-1) data sample collected with the Belle detector at the KEKB e(+)e(-) collider. The differential cross sections are fitted in the energy region 1.7 GeV < W < 2.5 GeV to confirm the two-photon production of two pions in the G wave. In the higher-energy region, we observe production of the chi(c0) charmonium state and obtain the product of its two-photon decay width and branching fraction to pi(0)pi(0). We also compare the observed angular dependence and ratios of cross sections for neutral-pion and charged-pion pair production to QCD models. The energy and angular dependence above 3.1 GeV are compatible with those measured in the pi(+)pi(-) channel, and in addition we find that the cross section ratio, sigma(pi(0)pi(0))/sigma(pi(+)pi(-)), is 0.32 +/- 0.03 +/- 0.05 on average in the 3.1-4.1 GeV region.
118755762
About the creation of proton–antiproton pair at electron–positron collider in the energy range of ψ(3770) mass
The process of electron positron annihilation into proton-antiproton pair is considered within the vicinity of psi(3770) resonance. The interference between the pure electromagnetic intermediate state and the psi(3770) state is evaluated. It is shown that this interference is destructive and the relative phase between these two contributions is large (phi(0) approximate to 250 degrees). (C) 2014 The Authors. Published by Elsevier B.V.
15056774
NN interactions in the extended chiral SU(3) quark model
Abstract The chiral SU (3) quark model is extended to include coupling between vector chiral field and quarks. By using this model, the phase shifts of NN scattering for different partial waves are studied. The results are very similar to those of the chiral SU (3) quark model calculation, in which one gluon exchange (OGE) plays dominate role in the short range part of the quark–quark interactions. Only in the 1 S 0 case, the one channel phase shifts of the extended chiral SU (3) quark model are obviously improved.
117987940
Parton's picture of the electroweak processes in high-energy e+ e- collisions
5737444
UNIVERSAL PHASE BETWEEN STRONG AND EM INTERACTIONS
It is shown that the experimental data of psi(3686) and psi(3770) are consistent with a -90 degree phase between the strong and eletromagnetic decay amplitudes. The e+ e- -> rho-pi measured at psi(3770) is also consistent with the branching ratio predicted by Rosner's scenario on rho-pi puzzle in charmonium physics. This scenario leads to a possible large charmless branching ratio in psi(3770) decays.