2350615
Constraining dark matter models from a combined analysis of Milky Way satellites with the Fermi Large Area Telescope.
Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Including the uncertainty in the dark matter distribution, robust upper limits are placed on dark matter annihilation cross sections. The 95% confidence level upper limits range from about 10(-26)  cm3  s(-1) at 5 GeV to about 5×10(-23)   cm3  s(-1) at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section (∼3×10(-26)  cm3  s(-1) for a purely s-wave cross section), without assuming additional boost factors.
121930739
Searches for cosmic-ray electron anisotropies with the Fermi Large Area Telescope
The Large Area Telescope on board the Fermi satellite (Fermi LAT) detected more than 1.6 x 10(6) cosmic-ray electrons/positrons with energies above 60 GeV during its first year of operation. The ar ...
207767119
Gamma-ray emission concurrent with the nova in the symbiotic binary V407 Cygni.
Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce pi(0) decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.
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.
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.
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.
116537829
Search for the decay $B^0\to DK^{*0}$ followed by $D\to K^-\pi^+$
We report a study of the decay $B^0\rightarrow D K^+\pi^-$ followed by $D\rightarrow K^-\pi^+$, where $D$ indicates $D^0$ or $\bar{D}^0$. We reconstruct the $D K^+\pi^-$ state in a phase space corresponding to $D K^{*}(892)^0$. The CP-violating angle $\phi_3$ affects its decay rate via the interference between $b\rightarrow u$ and $b\rightarrow c$ transitions. The result is obtained from a 711 ${\rm fb}^{-1}$ data sample that contains 772 $\times 10^6 B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We measure the ratio ${\cal R}_{DK^{*0}} \equiv \Gamma(B^0\rightarrow [K^-\pi^+]_DK^+\pi^-)/\Gamma(B^0\rightarrow [K^+\pi^-]_DK^+\pi^-)$ to be $(4.1 ^{+ 5.6 + 2.8}_{- 5.0 - 1.8}) \times 10^{-2}$, and set an upper limit of ${\cal R}_{DK^{*0}} < 0.16$ at the 95% confidence level.
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.
120509600
The Upper limit of the e+ e- partial width of X(3872)
Abstract The e + e − decay partial width of the recently observed state, X (3872), is estimated using the ISR data collected at s =4.03  GeV in e + e − annihilation experiment by BES at BEPC. It is found that Γ e + e − B π + π − J/ψ  eV at 90% C.L. if the J PC of X (3872) is 1 −− . Together with the potential models and other information, we conclude that X (3872) is very unlikely to be a vector state.
115461822
Observation of $e^+e^- \to \pi^+ \pi^- \pi^0 \chi_{bJ}$ and Search for $X_b \to \omega \Upsilon(1S)$ at $\sqrt{s}=10.867$ GeV
The $e^+e^- \to \pi^+ \pi^- \pi^0 \chi_{bJ}$ ($J=0,~1,~2$) processes are studied using a 118~fb$^{-1}$ data sample collected at a center-of-mass energy of 10.867 GeV, in the $\Upsilon(10860)$ energy range, with the Belle detector. The $\pi^+ \pi^- \pi^0 \chi_{b1}$, $\pi^+\pi^-\pi^0\chi_{b2}$, $\omega\chi_{b1}$ signals and the evidence of $\omega\chi_{b2}$ are observed for the first time and the cross sections are measured. No significant $\pi^+\pi^-\pi^0\chi_{b0}$ or $\omega\chi_{b0}$ signal is observed and 90\% confidence level upper limits on the cross sections for these two processes are obtained. In the $\pi^+\pi^-\pi^0$ invariant mass spectrum, significant non-$\omega$ signals are also observed. We search for the $X(3872)$-like state with a hidden $b\bar{b}$ component (named $X_b$) decaying into $\omega \Upsilon(1S)$; no significant signal is observed with a mass between $10.55$ and $10.65$ GeV/$c^2$.
53723212
Search for doubly charmed baryons and study of charmed strange baryons at Belle
We report results of a study of doubly charmed baryons and charmed strange baryons. The analysis is performed using a 980 fb(-1) data sample collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We search for doubly charmed baryons Xi(+(+))(cc) with the Lambda(+)(c) K- pi(+)(pi(+) ) and. Xi(0)(c) pi(+)(pi(+)) final states. No significant signal is observed. We also search for two excited charmed strange baryons, Xi(c)(3055)(+) and Xi(c)(3123)(+) with the Sigma(++)(c)(2455)K- and Sigma(++)(c)(2520)K- final states. The Xi(c)(3055)(+) signal is observed with a significance of 6.6 standard deviations including systematic uncertainty, while no signature of the Xi(c)(3123)(+) is seen. We also study properties of the Xi(c)(2645)(+) and measure a width of 2.6 +/- 0.2(stat) +/- 0.4(syst) MeV/c(2), which is the first significant determination.