124 research outputs found

    Monte Carlo study of particle production in diffractive proton-proton collisions at s\sqrt s = 13 TeV with the very forward detector combined with central information

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    Very forward (VF) detectors in hadron colliders, having unique sensitivity to diffractive processes, can be a powerful tool for studying diffractive dissociation by combining them with central detectors. Several Monte Carlo simulation samples in pp-pp collisions at s=13\sqrt s = 13 TeV were analyzed, and different nondiffractive and diffractive contributions were clarified through differential cross sections of forward neutral particles. Diffraction selection criteria in the VF-triggered-event samples were determined by using the central track information. The corresponding selection applicable in real experiments has \approx100% purity and 30%-70% efficiency. Consequently, the central information enables classification of the forward productions into diffraction and nondiffraction categories; in particular, most of the surviving events from the selection belong to low-mass diffraction events at log10(ξx)<5.5\log_{10}(\xi_{x}) < -5.5. Therefore, the combined method can uniquely access the low-mass diffraction regime experimentally.Comment: 10 pages, 16 figures, 1table

    The LHCf experiment at LHC

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    The LHCf experiment will be installed in 2007 on the LHC collider in the forward direction at ±140m from the ATLAS interaction point. The purpose of LHCf is to precisely measure the pion production cross section near zero degrees through the measurement of the photons produced in neutral pion decay. This measurement is crucial for the simulation of the showers induced in the atmosphere by very high energy cosmic rays; the 14 TeV energy available in the center of mass frame corresponds in fact to an equivalent energy of 1017 eV in the laboratory system. The paper focus on the proposed experiment and on the physics results that we expect from it

    Free-Floating planet Mass Function from MOA-II 9-year survey towards the Galactic Bulge

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    We present the first measurement of the mass function of free-floating planets (FFP) or very wide orbit planets down to an Earth mass, from the MOA-II microlensing survey in 2006-2014. Six events are likely to be due to planets with Einstein radius crossing times, tE<0.5t_{\rm E}<0.5days, and the shortest has tE=0.057±0.016t_{\rm E} = 0.057\pm 0.016days and an angular Einstein radius of θE=0.90±0.14μ\theta_{\rm E} = 0.90\pm 0.14\muas. We measure the detection efficiency depending on both tEt_{\rm E} and θE\theta_{\rm E} with image level simulations for the first time. These short events are well modeled by a power-law mass function, dN4/dlogM=(2.181.40+0.52)×(M/8M)α4dN_4/d\log M = (2.18^{+0.52}_{-1.40})\times (M/8\,M_\oplus)^{-\alpha_4} dex1^{-1}star1^{-1} with α4=0.960.27+0.47\alpha_4 = 0.96^{+0.47}_{-0.27} for M/M<0.02M/M_\odot < 0.02. This implies a total of f=2113+23f= 21^{+23}_{-13} FFP or very wide orbit planets of mass 0.33<M/M<66600.33<M/M_\oplus < 6660 per star, with a total mass of 8047+73M80^{+73}_{-47} M_\oplus per star. The number of FFPs is 1913+2319_{-13}^{+23} times the number of planets in wide orbits (beyond the snow line), while the total masses are of the same order. This suggests that the FFPs have been ejected from bound planetary systems that may have had an initial mass function with a power-law index of α0.9\alpha\sim 0.9, which would imply a total mass of 17152+80M171_{-52}^{+80} M_\oplus star1^{-1}. This model predicts that Roman Space Telescope will detect 988566+1848988^{+1848}_{-566} FFPs with masses down to that of Mars (including 575424+1733575^{+1733}_{ -424} with 0.1M/M10.1 \le M/M_\oplus \le 1). The Sumi(2011) large Jupiter-mass FFP population is excluded.Comment: 17 pages, 7 figures, accepted for publication in A

    Forward photon energy spectrum at LHC 7 TeV p-p collisions measured by LHCf

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    Abstract The LHCf experiment is one of the LHC forward experiments. The aim is to measure the energy and the transverse momentum spectra of photons, neutrons and π 0 's at the very forward region (the pseudo-rapidity range of η > 8.4 ), which should be critical data to calibrate hadron interaction models used in the air shower simulations. LHCf successfully operated at s = 900 GeV and s = 7 TeV proton–proton collisions in 2009 and 2010. We present the first physics result, single photon energy spectra at s = 7 TeV proton–proton collisions and the pseudo-rapidity ranges of η > 10.94 and 8.81 η 8.9 . The obtained spectra were compared with the predictions by several hadron interaction models and the models do not reproduce the experimental results perfectly