LHC optics and elastic scattering measured by the TOTEM experiment

The TOTEM experiment at the LHC has measured proton-proton elastic scattering in dedicated runs at $\sqrt{s}=7$ and 8 TeV centre-of-mass LHC energies. The proton-proton total cross-section $\sigma_{\rm tot}$ has been derived for both energies using a luminosity independent method. TOTEM has excluded a purely exponential differential cross-section for elastic proton-proton scattering with significance greater than 7$\sigma$ in the $|t|$ range from 0.027 to 0.2 GeV$^{2}$ at $\sqrt{s}=8$ TeV.Comment: Proceedings, 17th Lomonosov Conferenc

Elastic scattering of protons at the TOTEM experiment at the LHC

The TOTEM experiment at the LHC at CERN is optimized to measure elastic and diffractive scattering at the LHC and measures the total proton-proton cross-section with the luminosity-independent method. The TOTEM experiment uses the special technique of movable beam pipe insertions -- called Roman Pots -- to detect very forward protons. The reconstruction of the forward proton kinematics requires the precise understanding of the LHC beam optics. A new method of LHC optics determination is reported, which exploits kinematical distributions of elastically scattered proton-proton data measured by the Roman Pots of the TOTEM experiment. The method has been successfully applied to data samples recorded since 2010. The interpretation of the proton-proton elastic differential cross-section is a challenging task. The geometrical model of proton-proton elastic scattering of Bialas and Bzdak is fitted to ISR data and to data measured by the TOTEM experiment at LHC energy of $\sqrt{s}=7$~TeV. The Bialas-Bzdak model is generalized and improved in order to give a satisfactory and unified description of the ISR and LHC data. The improved model is extrapolated to future LHC energies and beyond

Measurement of the forward charged particle pseudorapidity density in pp collisions at √s=8 TeV using a displaced interaction point

The pseudorapidity density of charged particles dN(ch)/deta is measured by the TOTEM experiment in pp collisions at sqrt(s) = 8 TeV within the range 3.9 0 MeV/c, produced in inelastic interactions with at least one charged particle in -7 < eta < -6 or 3.7 < eta <4.8 . The dN(ch)/deta has been found to decrease with |eta|, from 5.11 +- 0.73 at eta = 3.95 to 1.81 +- 0.56 at eta= - 6.925. Several MC generators are compared to the data and are found to be within the systematic uncertainty of the measurement

Measurement of elastic pp scattering at √s=8 TeV in the Coulomb–nuclear interference region: determination of the ρ -parameter and the total cross-section

The TOTEM experiment at the CERN LHC has measured elastic proton-proton scattering at the centre-of- mass energy √s = 8 TeV and four-momentum transfers squared, |t|, from 6 × 10−4 GeV2 to 0.2 GeV2. Near the lower end of the t-interval the differential cross-section is sensitive to the interference between the hadronic and the electromagnetic scattering amplitudes. This article presents the elastic cross-section measurement and the constraints it imposes on the functional forms of the modulus and phase of the hadronic elastic amplitude. The data exclude the tradi- tional Simplified West and Yennie interference formula that requires a constant phase and a purely exponential modu- lus of the hadronic amplitude. For parametrisations of the hadronic modulus with second- or third-order polynomials in the exponent, the data are compatible with hadronic phase functions giving either central or peripheral behaviour in the impact parameter picture of elastic scattering. In both cases, the ρ-parameter is found to be 0.12 ± 0.03. The results for the total hadronic cross-section are σtot = (102.9 ± 2.3) mb and (103.0 ± 2.3) mb for central and peripheral phase for- mulations, respectively. Both are consistent with previous TOTEM measurements

First measurement of elastic, inelastic and total cross-section at √s=13 TeV by TOTEM and overview of cross-section data at LHC energies: TOTEM Collaboration

The TOTEM collaboration has measured the proton-proton total cross section at $\sqrt{s}=13$ TeV with a luminosity-independent method. Using dedicated $\beta^{*}=90$ m beam optics, the Roman Pots were inserted very close to the beam. The inelastic scattering rate has been measured by the T1 and T2 telescopes during the same LHC fill. After applying the optical theorem the total proton-proton cross section is $\sigma_{\rm tot}=(110.6 \pm 3.4$) mb, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity-independent elastic and inelastic cross sections: $\sigma_{\rm el} = (31.0 \pm 1.7)$ mb and $\sigma_{\rm inel} = (79.5 \pm 1.8)$ mb

Magyar Tanítóképző 55 (1942) 7

Magyar Tanítóképző A Tanítóképző-intézeti Tanárok Országos Egyesületének folyóirata 55. évfolyam, 7. szám Budapest, 1942. júliu

Search for flavor-changing neutral current interactions of the top quark and the Higgs boson decaying to a bottom quark-antiquark pair at root s=13 TeV

A search for flavor-changing neutral current interactions of the top quark (t) and the Higgs boson (H) is presented. The search is based on a data sample corresponding to an integrated luminosity of 137 fb(-1) recorded by the CMS experiment at the LHC in proton-proton collisions at root s = 13TeV. Events containing exactly one lepton (muon or electron) and at least three jets, among which at least two are identified as originating from the hadronization of a bottom quark, are analyzed. A set of deep neural networks is used for kinematic event reconstruction, while boosted decision trees distinguish the signal from the background events. No significant excess over the background predictions is observed, and upper limits on the signal production cross sections are extracted. These limits are interpreted in terms of top quark decay branching fractions (B) to the Higgs boson and an up (u) or a charm quark (c). Assuming one nonvanishing extra coupling at a time, the observed (expected) upper limits at 95% confidence level are B(t -> Hu) Hc) < 0.094 (0.086)%