Precise measurement of the total cross section and the Coulomb scattering at the LHC

A precise measurement of the total cross section and the coulomb scattering at the LHC requires the observation of elastically scatteredparticles at extremely small angles (14 microrad, -t < 0.01 GeV**2 for the first case; 3 microrad, -t<0.0006 GeV**2 for the second one). In this paper a very high-beta insertion optics is presented. A feasibility study, including the acceptance of the detectors, for an experiment to be installed in IR1 or IR5, is also presented.Comment: 3 pages, 4 figures, 7th European Particle Accelator Conferenc

A Very High-beta Optics to be used for an Absolute Luminosity Determination with Forward Detectors in ATLAS

The Atlas experiment at the LHC pursues a number of different approaches to obtain an estimate of the absolute luminosity [3]. Measuring elastic scattering at very small angles (3 μrad) represents a different and complimentary approach that will improve the precision of the final luminosity estimate. In this paper we show the required very high-β optics and the detector acceptance studies

Infrared Imaging of Capella with the IOTA Closure Phase Interferometer

We present infrared aperture synthesis maps produced with the upgraded IOTA interferometer. Michelson interferograms on the close binary system Capella (Alpha Aur) were obtained in the H-band between 2002 November 12 and 16 using the IONIC3 beam combiner. With baselines of 15m < B < 38m, we were able to determine the relative position of the binary components with milliarcsecond (mas) precision and to track their movement along the approx. 14 degree arc covered by our observation run. We briefly describe the algorithms used for visibility and closure phase estimation. Three different Hybrid Mapping and Bispectrum Fitting techniques were implemented within one software framework and used to reconstruct the source brightness distribution. By dividing our data into subsets, the system could be mapped at three epochs, revealing the motion of the stars. The precise position of the binary components was also determined with model fits, which in addition revealed I_Aa/I_Ab=1.49 +/- 0.10 and apparent stellar uniform-disk (UD) diameters of Theta_Aa=8.9 +/- 0.6 mas and Theta_Ab=5.8 +/- 0.8 mas. To improve the u, v-plane coverage, we compensated this orbital motion by applying a rotation-compensating coordinate transformation. The resulting model-independent map with a beam size of 5.4 x 2.6 mas allows the resolution of the stellar surfaces of the Capella giants themselves.Comment: Accepted by the Astronomical Journal (2005-03-21

An infrared integrated optic astronomical beam combiner for stellar interferometry at 3-4 microns

Integrated-optic, astronomical, two-beam and three-beam, interferometric combiners have been designed and fabricated for operation in the L band (3 - 4 microns) for the first time. The devices have been realized in titanium-indiffused, x-cut lithium niobate substrates, and on-chip electro-optic fringe scanning has been demonstrated. White light fringes were produced in the laboratory using the two-beam combiner integrated with an on-chip Y-splitter.Comment: This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/oe. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under la

Integrated optics for astronomical interferometry - VI. Coupling the light of the VLTI in K band

Our objective is to prove that integrated optics (IO) is not only a good concept for astronomical interferometry but also a working technique with high performance. We used the commissioning data obtained with the dedicated K-band integrated optics two-telescope beam combiner which now replaces the fiber coupler MONA in the VLTI/VINCI instrument. We characterize the behaviour of this IO device and compare its properties to other single mode beam combiner like the previously used MONA fiber coupler. The IO combiner provides a high optical throughput, a contrast of 89% with a night-to-night stability of a few percent. Even if a dispersive phase is present, we show that it does not bias the measured Fourier visibility estimate. An upper limit of 0.005 for the cross-talk between linear polarization states has been measured. We take advantage of the intrinsic contrast stability to test a new astronomical prodecure for calibrating diameters of simple stars by simultaneously fitting the instrumental contrast and the apparent stellar diameters. This method reaches an accuracy with diameter errors of the order of previous ones but without the need of an already known calibrator. These results are an important step of integrated optics and paves the road to incoming imaging interferometer projects

The performance of the LHCf detector for hadronic showers

The Large Hadron Collider forward (LHCf) experiment has been designed to use the LHC to benchmark the hadronic interaction models used in cosmic-ray physics. The LHCf experiment measures neutral particles emitted in the very forward region of LHC collisions. In this paper, the performances of the LHCf detectors for hadronic showers was studied with MC simulations and beam tests. The detection efficiency for neutrons is from 60% to 70% above 500 GeV. The energy resolutions are about 40% and the position resolution is 0.1 to 1.3mm depend on the incident energy for neutrons. The energy scale determined by the MC simulations and the validity of the MC simulations were examined using 350 GeV proton beams at the CERN-SPS.Comment: 15pages, 19 figure

Measurement of forward photon production cross-section in proton-proton collisions at s\sqrt{s} = 13 TeV with the LHCf detector

In this paper, we report the production cross-section of forward photons in the pseudorapidity regions of $\eta\,>\,10.94$ and $8.99\,>\,\eta\,>\,8.81$, measured by the LHCf experiment with proton--proton collisions at $\sqrt{s}$ = 13 TeV. The results from the analysis of 0.191 $\mathrm{nb^{-1}}$ of data obtained in June 2015 are compared to the predictions of several hadronic interaction models that are used in air-shower simulations for ultra-high-energy cosmic rays. Although none of the models agree perfectly with the data, EPOS-LHC shows the best agreement with the experimental data among the models.Comment: 21 pages, 4 figure

Double Spin Asymmetries A_NN and A_SS at sqrt{s}=200 GeV in Polarized Proton-Proton Elastic Scattering at RHIC

We present the first measurements of the double spin asymmetries A_NN and A_SS at sqrt{s}=200 GeV, obtained by the pp2pp experiment using polarized proton beams at the Relativistic Heavy Ion Collider (RHIC). The data were collected in the four momentum transfer t range 0.01<|t|<0.03 (GeV/c)^2. The measured asymmetries, which are consistent with zero, allow us to estimate upper limits on the double helicity-flip amplitudes phi_2 and phi_4 at small t as well as on the difference Delta(sigma_T) between the total cross sections for transversely polarized protons with antiparallel or parallel spin orientations.Comment: 13 pages with 3 figures. Final version accepted by Phys. Lett.

First Measurement of A_N at sqrt(s)=200 GeV in Polarized Proton-Proton Elastic Scattering at RHIC

We report on the first measurement of the single spin analyzing power (A_N) at sqrt(s)=200GeV, obtained by the pp2pp experiment using polarized proton beams at the Relativistic Heavy Ion Collider (RHIC). Data points were measured in the four momentum transfer t range 0.01 < |t| < 0.03 (GeV/c)^2. Our result, averaged over the whole t-interval is about one standard deviation above the calculation, which uses interference between electromagnetic spin-flip amplitude and hadronic non-flip amplitude, the source of A_N. The difference could be explained by an additional contribution of a hadronic spin-flip amplitude to A_N.Comment: 13 pages, 5 figures. New values of polarization errors. Final version submitted to Phys. Lett.

Measurement of forward neutral pion transverse momentum spectra for s\sqrt{s} = 7TeV proton-proton collisions at LHC

The inclusive production rate of neutral pions in the rapidity range greater than $y=8.9$ has been measured by the Large Hadron Collider forward (LHCf) experiment during LHC $\sqrt{s}=7$\,TeV proton-proton collision operation in early 2010. This paper presents the transverse momentum spectra of the neutral pions. The spectra from two independent LHCf detectors are consistent with each other and serve as a cross check of the data. The transverse momentum spectra are also compared with the predictions of several hadronic interaction models that are often used for high energy particle physics and for modeling ultra-high-energy cosmic-ray showers.Comment: 18 Pages, 10 figures, submitted to Phys. Rev.