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First measurement of elastic, inelastic and total cross-section at $$\sqrt{s}=13$$ 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 s√=13 TeV with a luminosity-independent method. Using dedicated β*=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 σ tot =(110.6 ± 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 σ el =(31.0 ± 1.7) mb and σ inel =(79.5 ± 1.8) mb .
Analysis of a GaN-Based CRM Totem-Pole PFC Converter Considering Current Sensing Delay
High-frequency soft-switched gallium-nitride (GaN) based critical conduction mode (CRM) totem-pole power factor correction (PFC) converter is one of the most potential candidates in data center power supplies. However, the high-speed cycle-by-cycle zero current detection (ZCD) brings challenges to zero-voltage-switching (ZVS) control. Current sensing delay (CSD) exists, and the ZCD circuit is sensitive to high di/dt switching noise. In this paper, mechanisms of the ZCD time error are elaborated, and impacts of the current sensing delay on converter switching frequency, inductor current, input current third harmonic distortion (THD), and power loss are analyzed. Qualification time is added within the controller for immunity to the swiching noise, and a CSD embedded converter model is proposed to compensate the ZCD time delay. Also, loss modeling of the CRM totem-pole PFC is conducted to aid in analysis of the proposed theory. A 1.5 kW single-phase CRM totem-pole PFC prototype is tested. Experimental results validiate the analysis, modeling, and the proposed compensation method for current sensing delay.
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 √s = 8 TeV based on a high-statistics data sample obtained with the β* = 90 m 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 σ. Two extended parametrisations, with quadratic and cubic polynomials in the exponent, are shown to be well compatible with the data. As a result, 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.
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. In conclusion, 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.
Elastic differential cross-section measurement at $\sqrt{s}=13$ TeV by TOTEM
The TOTEM collaboration has measured the elastic proton-proton differential cross section dσ/d t at √s = 13 TeV LHC energy using dedicated β* = 90 m beam optics. The Roman Pot detectors were inserted to 10σ distance from the LHC beam, which allowed the measurement of the range [0.04 GeV 2 ; 4 GeV 2 ] in four-momentum transfer squared | t |. The efficient data acquisition allowed to collect about 10 9 elastic events to precisely measure the differential cross-section including the diffractive minimum (dip), the subsequent maximum (bump) and the large-| t | tail. The average nuclear slope has been found to be B = (20.40 ± 0.002 stat ± 0.01syst) GeV –2 in the | t |-range 0.04–0.2 GeV 2 . The dip position is | t dip | = (0.47 ± 0.004 stat ± 0.01 syst ) GeV 2 . The differential cross section ratio at the bump vs. at the dip R = 1.77 ± 0.01 stat has been measured with high precision. The series of TOTEM elastic pp measurements show that the dip is a permanent feature of the pp differential cross-section at the TeV scale.
Observation of proton-tagged, central (semi)exclusive production of high-mass lepton pairs in pp collisions at 13 TeV with the CMS-TOTEM precision proton spectrometer
The process pp → pℓ$^{+}$ℓ$^{−}$p$^{(*)}$, with ℓ$^{+}$ℓ$^{−}$ a muon or an electron pair produced at midrapidity with mass larger than 110 GeV, has been observed for the first time at the LHC in pp collisions at $ \sqrt{s}=13 $ TeV. One of the two scattered protons is measured in the CMS-TOTEM precision proton spectrometer (CT-PPS), which operated for the first time in 2016. The second proton either remains intact or is excited and then dissociates into a low-mass state p$^{*}$, which is undetected. The measurement is based on an integrated luminosity of 9.4 fb$^{−1}$ collected during standard, high-luminosity LHC operation. A total of 12 μ$^{+}$μ$^{−}$ and 8 e$^{+}$e$^{−}$ pairs with m(ℓ$^{+}$ℓ$^{−}$) > 110 GeV, and matching forward proton kinematics, are observed, with expected backgrounds of 1.49 ± 0.07 (stat) ± 0.53 (syst) and 2.36 ± 0.09 (stat) ± 0.47 (syst), respectively. This corresponds to an excess of more than five standard deviations over the expected background. The present result constitutes the first observation of proton-tagged γγ collisions at the electroweak scale. This measurement also demonstrates that CT-PPS performs according to the design specifications.
First data from TOTEM experiment at LHC
The TOTEM experiment at the LHC is mainly dedicated to the measurement of the total proton-proton cross section, elastic scattering and to the study of the diffractive processes. This contribution reviews the physics goals of the experiment, the status of the experimental apparatus and of the analysis of the first data from the LHC.
Totem results
The TOTEM experiment measured the elastic, inelastic and total pp cross-section at √(s)=7 TeV and 8 TeV. The elastic scattering was measured in a large range of |t| allowing the determination of the pp cross-section, the discrimination among the elastic models, and the study of the Coulomb-Nuclear interference. The measurements of the charged particle dN{sub CH}/dη and on single and double diffractive interactions are also reported.
Proton reconstruction with the CMS-TOTEM Precision Proton Spectrometer
The Precision Proton Spectrometer (PPS) of the CMS and TOTEM experiments collected 107.7 fb$^{-1}$ in proton-proton (pp) collisions at the LHC at 13 TeV (Run 2). This paper describes the key features of the PPS alignment and optics calibrations, the proton reconstruction procedure, as well as the detector efficiency and the performance of the PPS simulation. The reconstruction and simulation are validated using a sample of (semi)exclusive dilepton events. The performance of PPS has proven the feasibility of continuously operating a near-beam proton spectrometer at a high luminosity hadron collider.
Proton reconstruction with the TOTEM Roman pot detectors for high- β * LHC data
The TOTEM Roman pot detectors are used to reconstruct the transverse momentum of scattered protons and to estimate the transverse location of the primary interaction. This paper presents new methods of track reconstruction, measurements of strip-level detection efficiencies, cross-checks of the LHC beam optics, and detector alignment techniques, along with their application in the selection of signal collision events. The track reconstruction is performed by exploiting hit cluster information through a novel method using a common polygonal area in the intercept-slope plane. The technique is applied in the relative alignment of detector layers with μm precision. A tag-and-probe method is used to extract strip-level detection efficiencies. The alignment of the Roman pot system is performed through time-dependent adjustments, resulting in a position accuracy of 3 μm in the horizontal and 60 μm in the vertical directions. The goal is to provide an optimal reconstruction tool for central exclusive physics analyses based on the high-β* data-taking period at $\sqrt({s})$ = 13 TeV in 2018.
Holographic odderon at TOTEM?
We consider the contribution of the Odderon to diffractive p p and p p ¯ elastic scattering at large center of mass energy. We identify the Odderon and Pomeron with the Reggeized 1 ± − and 2 + + glueballs in the bulk, respectively. We use for the gravity dual description the repulsive wall model, to account for the proper Gribov diffusion for off-forward scattering. The eikonalized and unitarized amplitudes exhibit a vanishingly small rho-parameter, and a slope parameter fixed by twice the closed string slope. The results for the differential and total cross sections are compared to the empirical results reported recently by the TOTEM collaboration. Published by the American Physical Society 2024
Multi-phase Coupled and Integrated Inductors for Critical Conduction Mode Totem-Pole PFC Converter
Coupled inductor has been widely used in voltage regulator (VR) applications for many years because it can help reducing current ripple and improving transient performance. In this paper, the coupled inductor concept is applied to interleaved totem-pole critical conduction mode (CRM) PFC converter for 6.6kW on board battery charger. The difference between negative coupling and positive coupling will be discussed. The benefit of positive coupling for battery charger will be presented, such as reducing switching frequency range and reducing input differential mode (DM) noise. In addition, balance technique is applied to help minimize common mode (CM) noise. Last but not least, the inductor will be integrated into PCB winding with a little sacrifice on loss. With the inductor integration, the converter can avoid labor intensive production and achieve fully automated manufacture. The analysis is verified by both simulation and experiment.
Measurement of pseudorapidity distributions of charged particles in proton-proton collisions at $\sqrt{s}$ = 8 TeV by the CMS and TOTEM experiments
Pseudorapidity (η) distributions of charged particles produced in proton–proton collisions at a centre-of-mass energy of 8 TeV are measured in the ranges |η|<2.2 and 5.3<|η|<6.4 covered by the CMS and TOTEM detectors, respectively. We found that the data correspond to an integrated luminosity of L=45 μb -1 . These measurements are presented for three event categories. The most inclusive category is sensitive to 91–96 % of the total inelastic proton–proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single diffractive dissociation events. Finally, the data are compared to models used to describe high-energy hadronic interactions. None of the models considered provide a consistent description of the measured distributions.
Measurement of single-diffractive dijet production in proton-proton collisions at $\sqrt{s} =$ 8 TeV with the CMS and TOTEM experiments
Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss $\xi $ and the four-momentum transfer squared t. Both processes ${\text{ p }{}{}} {\text{ p }{}{}} \rightarrow {\text{ p }{}{}} {\text{ X }} $ and ${\text{ p }{}{}} {\text{ p }{}{}} \rightarrow {\text{ X }} {\text{ p }{}{}} $, i.e. with the proton scattering to either side of the interaction point, are measured, where ${\text{ X }} $ includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton–proton collisions at $\sqrt{s} = 8\,\text {Te}\text {V} $ during a dedicated run with $\beta ^{*} = 90\,\text {m} $ at low instantaneous luminosity and correspond to an integrated luminosity of $37.5{\,\text {nb}^{-1}} $. The single-diffractive dijet cross section $\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}$, in the kinematic region $\xi < 0.1$, $0.03< |t | < 1\,\text {Ge}\text {V} ^2$, with at least two jets with transverse momentum $p_{\mathrm {T}} > 40\,\text {Ge}\text {V} $, and pseudorapidity $|\eta | < 4.4$, is $21.7 \pm 0.9\,\text {(stat)} \,^{+3.0}_{-3.3}\,\text {(syst)} \pm 0.9\,\text {(lumi)} \,\text {nb} $. The ratio of the single-diffractive to inclusive dijet yields, normalised per unit of $\xi $, is presented as a function of x, the longitudinal momentum fraction of the proton carried by the struck parton. The ratio in the kinematic region defined above, for x values in the range $-2.9 \le \log _{10} x \le -1.6$, is $R = (\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}/\Delta \xi )/\sigma _{\mathrm {jj}} = 0.025 \pm 0.001\,\text {(stat)} \pm 0.003\,\text {(syst)} $, where $\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}$ and $\sigma _{\mathrm {jj}}$ are the single-diffractive and inclusive dijet cross sections, respectively. The results are compared with predictions from models of diffractive and nondiffractive interactions. Monte Carlo predictions based on the HERA diffractive parton distribution functions agree well with the data when corrected for the effect of soft rescattering between the spectator partons.
A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer
A generic search is presented for the associated production of a Z boson or a photon with an additional unspecified massive particle X, pp → pp + Z/γ + X, in proton-tagged events from proton–proton collisions at $\sqrt{s}$ = 13 TeV, recorded in 2017 with the CMS detector and the CMS-TOTEM precision proton spectrometer. The missing mass spectrum is analysed in the 600–1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant excess in data with respect to the background predictions has been observed. Model-independent upper limits on the visible pro duction cross section of pp → pp + Z/γ + X are set
The CMS-TOTEM Precision Proton Spectrometer: CT-PPS
The CMS-TOTEM Precison Proton Spectrometer, CT-PPS, is an approved project to add 3D silicon tracking and quartz Cherenkov timing detectors in Roman pots at z = ±204-215 m from the CMS collision point to study final states p+X + p. The central state X can be aW-pair from a photon-photon interaction, high ET jets from gluon collisions, etc., with M(X) obtained directly as well as from the two outgoing protons. The project is designed to operate at high luminosity, with up to about 50 interactions per 25 ns bunch crossing, and to be fully operational for physics in 2016.