Raman and Computational Study on the Adsorption of Xanthine on Silver Nanocolloids

Xanthine is a nucleobase, deriving from adenine and guanine by deamination and oxidation processes, which may deposit in the human body causing diseases, similar to uric acid. Here, we have investigated the adsorption of xanthine on silver colloidal nanoparticles by means of surface-enhanced Raman scattering (SERS) with an exciting radiation in the near-infrared spectral region, where interference due to fluorescence does not occur, along with density functional theory calculations of molecule/metal model systems. By adopting a combined experimental and computational approach, we have identified the "marker" SERS bands of xanthine and the tautomer that preferentially binds the silver particles, as well as the molecular group involved in the interaction with metal. This investigation allows using the FT-SERS spectroscopy for biosensory and diagnostic purposes in body fluids, detecting abnormal levels of xanthine, and preventing metabolic diseases

Type IIB Holographic Superfluid Flows

We construct fully backreacted holographic superfluid flow solutions in a five-dimensional theory that arises as a consistent truncation of low energy type IIB string theory. We construct a black hole with scalar and vector hair in this theory, and study the phase diagram. As expected, the superfluid phase ceases to exist for high enough superfluid velocity, but we show that the phase transition between normal and superfluid phases is always second order. We also analyze the zero temperature limit of these solutions. Interestingly, we find evidence that the emergent IR conformal symmetry of the zero-temperature domain wall is broken at high enough velocity.Comment: v3: Published version. Figures 5 and 6 corrected. 24 pages, 7 figure

Elastic Scattering and Total Cross-Section in p+p reactions measured by the LHC Experiment TOTEM at sqrt(s) = 7 TeV

Proton-proton elastic scattering has been measured by the TOTEM experiment at the CERN Large Hadron Collider at $\sqrt{s} = 7$ TeV in special runs with the Roman Pot detectors placed as close to the outgoing beam as seven times the transverse beam size. The differential cross-section measurements are reported in the |t|-range of 0.36 to 2.5 GeV^2. Extending the range of data to low t values from 0.02 to 0.33 GeV^2,and utilizing the luminosity measurements of CMS, the total proton-proton cross section at sqrt(s) = 7 TeV is measured to be (98.3 +- 0.2(stat) +- 2.8(syst)) mb.Comment: Proceedings of the XLI International Symposium on Multiparticle Dynamics. Accepted for publication in Prog. Theor. Phy

Proton-proton elastic scattering at the LHC energy of {\surd} = 7 TeV

Proton-proton elastic scattering has been measured by the TOTEM experiment at the CERN Large Hadron Collider at {\surd}s = 7 TeV in dedicated runs with the Roman Pot detectors placed as close as seven times the transverse beam size (sbeam) from the outgoing beams. After careful study of the accelerator optics and the detector alignment, |t|, the square of four-momentum transferred in the elastic scattering process, has been determined with an uncertainty of d t = 0.1GeV p|t|. In this letter, first results of the differential cross section are presented covering a |t|-range from 0.36 to 2.5GeV2. The differential cross-section in the range 0.36 < |t| < 0.47 GeV2 is described by an exponential with a slope parameter B = (23.6{\pm}0.5stat {\pm}0.4syst)GeV-2, followed by a significant diffractive minimum at |t| = (0.53{\pm}0.01stat{\pm}0.01syst)GeV2. For |t|-values larger than ~ 1.5GeV2, the cross-section exhibits a power law behaviour with an exponent of -7.8_\pm} 0.3stat{\pm}0.1syst. When compared to predictions based on the different available models, the data show a strong discriminative power despite the small t-range covered.Comment: 12pages, 5 figures, CERN preprin

Performance of the TOTEM Detectors at the LHC

The TOTEM Experiment is designed to measure the total proton-proton cross-section with the luminosity-independent method and to study elastic and diffractive pp scattering at the LHC. To achieve optimum forward coverage for charged particles emitted by the pp collisions in the interaction point IP5, two tracking telescopes, T1 and T2, are installed on each side of the IP in the pseudorapidity region 3.1 < = |eta | < = 6.5, and special movable beam-pipe insertions - called Roman Pots (RP) - are placed at distances of +- 147 m and +- 220 m from IP5. This article describes in detail the working of the TOTEM detector to produce physics results in the first three years of operation and data taking at the LHC.Comment: 40 pages, 31 figures, submitted to Int. J. Mod. Phys.

LHC Optics Measurement with Proton Tracks Detected by the Roman Pots of the TOTEM Experiment

Precise knowledge of the beam optics at the LHC is crucial to fulfil the physics goals of the TOTEM experiment, where the kinematics of the scattered protons is reconstructed with the near-beam telescopes -- so-called Roman Pots (RP). Before being detected, the protons' trajectories are influenced by the magnetic fields of the accelerator lattice. Thus precise understanding of the proton transport is of key importance for the experiment. A novel method of optics evaluation is proposed which exploits kinematical distributions of elastically scattered protons observed in the RPs. Theoretical predictions, as well as Monte Carlo studies, show that the residual uncertainty of this optics estimation method is smaller than 0.25 percent.Comment: 20 pages, 11 figures, 5 figures, to be submitted to New J. Phy

Double diffractive cross-section measurement in the forward region at LHC

The first double diffractive cross-section measurement in the very forward region has been carried out by the TOTEM experiment at the LHC with center-of-mass energy of sqrt(s)=7 TeV. By utilizing the very forward TOTEM tracking detectors T1 and T2, which extend up to |eta|=6.5, a clean sample of double diffractive pp events was extracted. From these events, we measured the cross-section sigma_DD =(116 +- 25) mub for events where both diffractive systems have 4.7 <|eta|_min < 6.5 .Comment: 5 pages, 1 figure, submitted for publicatio

Defect studies of ZnO films prepared by pulsed laser deposition on various substrates

ZnO thin films deposited on various substrates were characterized by slow positron implantation spectroscopy (SPIS) combined with X-ray diffraction (XRD). All films studied exhibit wurtzite structure and crystallite size 20-100 nm. The mosaic spread of crystallites is relatively small for the films grown on single crystalline substrates while it is substantial for the film grown on amorphous substrate. SPIS investigations revealed that ZnO films deposited on single crystalline substrates exhibit significantly higher density of defects than the film deposited on amorphous substrate. This is most probably due to a higher density of misfit dislocations, which compensate for the lattice mismatch between the film and the substrate

Diamond Detectors for the TOTEM Timing Upgrade

This paper describes the design and the performance of the timing detector developed by the TOTEM Collaboration for the Roman Pots (RPs) to measure the Time-Of-Flight (TOF) of the protons produced in central diffractive interactions at the LHC. The measurement of the TOF of the protons allows the determination of the longitudinal position of the proton interaction vertex and its association with one of the vertices reconstructed by the CMS detectors. The TOF detector is based on single crystal Chemical Vapor Deposition (scCVD) diamond plates and is designed to measure the protons TOF with about 50 ps time precision. This upgrade to the TOTEM apparatus will be used in the LHC run 2 and will tag the central diffractive events up to an interaction pileup of about 1. A dedicated fast and low noise electronics for the signal amplification has been developed. The digitization of the diamond signal is performed by sampling the waveform. After introducing the physics studies that will most profit from the addition of these new detectors, we discuss in detail the optimization and the performance of the first TOF detector installed in the LHC in November 2015.Comment: 26 pages, 18 figures, 2 tables, submitted for publication to JINS

Evidence for non-exponential elastic proton-proton differential cross-section at low |t| and sqrt(s) = 8 TeV by TOTEM

The TOTEM experiment has made a precise measurement of the elastic proton-proton differential cross-section at the centre-of-mass energy sqrt(s) = 8 TeV based on a high-statistics data sample obtained with the beta* = 90 optics. Both the statistical and systematic uncertainties remain below 1%, except for the t-independent contribution from the overall normalisation. This unprecedented precision allows to exclude a purely exponential differential cross-section in the range of four-momentum transfer squared 0.027 < |t| < 0.2 GeV^2 with a significance greater than 7 sigma. Two extended parametrisations, with quadratic and cubic polynomials in the exponent, are shown to be well compatible with the data. Using them for the differential cross-section extrapolation to t = 0, and further applying the optical theorem, yields total cross-section estimates of (101.5 +- 2.1) mb and (101.9 +- 2.1) mb, respectively, in agreement with previous TOTEM measurements.Comment: Final version published in Nuclear Physics