Kentaro Kawade

In early 2010, the Large Hadron Collider forward (LHCf) experiment measured very forward neutral particle spectra in LHC proton–proton collisions. From a limited data set taken under the best beam conditions (low beam-gas background and low occurrence of pile-up events), the single photon spectra at s=7 TeV and pseudo-rapidity (η) ranges from 8.81 to 8.99 and from 10.94 to infinity were obtained for the first time and are reported in this Letter. The spectra from two independent LHCf detectors are consistent with one another and serve as a cross check of the data. The photon spectra are also compared with the predictions of several hadron interaction models that are used extensively for modeling ultra-high energy cosmic-ray showers. Despite conservative estimates for the systematic errors, none of the models agree perfectly with the measurements. A notable difference is found between the data and the DPMJET 3.04 and PYTHIA 8.145 hadron interaction models above 2 TeV where the models predict higher photon yield than the data. The QGSJET II-03 model predicts overall lower photon yield than the data, especially above 2 TeV in the rapidity range 8.81<η<8.99.

The differential cross sections for inclusive neutral pions as a function of transverse and longitudinal momentum in the very forward rapidity region have been measured at the Large Hadron Collider (LHC) with the Large Hadron Collider forward detector (LHCf) in proton-proton collisions at $\sqrt{s}=$ 2.76 and 7 TeV and in proton-lead collisions at nucleon-nucleon center-of-mass energies of $\sqrt{s_\text{NN}}=$ 5.02 TeV. Such differential cross sections in proton-proton collisions are compatible with the hypotheses of limiting fragmentation and Feynman scaling. Comparing proton-proton with proton-lead collisions, we find a sizable suppression of the production of neutral pions in the differential cross sections after subtraction of ultra-peripheral proton-lead collisions. This suppression corresponds to the nuclear modification factor value of about 0.1-0.3. The experimental measurements presented in this paper provide a benchmark for the hadronic interaction Monte Carlo simulation codes that are used for the simulation of cosmic ray air showers.

The Large Hadron Collider forward (LHCf) experiment is designed to use the LHC to verify the hadronic-interaction models used in cosmic-ray physics. Forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. We report the neutron-energy spectra for LHC $\sqrt{s}$ = 7 TeV proton--proton collisions with the pseudo-rapidity $\eta$ ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. The measured energy spectra obtained from the two independent calorimeters of Arm1 and Arm2 show the same characteristic feature before unfolding the difference in the detector responses. We unfolded the measured spectra by using the multidimensional unfolding method based on Bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. The QGSJET II-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results and the DPMJET 3.04 model describes our results well at the lower pseudo-rapidity ranges. However no model perfectly explains the experimental results in the whole pseudo-rapidity range. The experimental data indicate the most abundant neutron production rate relative to the photon production, which does not agree with predictions of the models.

The inclusive production rate of neutral pions in the rapidity range greater than y ¼ 8:9 has been measured by the Large Hadron Collider forward (LHCf) experiment during ffiffi ffi s p ¼ 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 ultrahigh-energy cosmic ray showers.

The inclusive photon energy spectra measured by the Large Hadron Collider forward (LHCf) experiment in the very forward region of LHC proton-proton collisions at $\sqrt{s}=$ 900 GeV are reported. The results from the analysis of 0.30 $\mathrm{nb^{-1}}$ of data collected in May 2010 in the two pseudorapidity regions of $\eta > 10.15$ and $8.77 < \eta < 9.46$ are compared with the predictions of the hadronic interaction models DPMJET 3.04, EPOS 1.99, PYTHIA 8.145, QGSJET I -.1em I-03 and SIBYLL 2.1, which are widely used in ultra-high-energy cosmic-ray experiments. EPOS 1.99 and SYBILL 2.1 show a reasonable agreement with the spectral shape of the experimental data, whereas they predict lower cross-sections than the data. The other models, DPMJET 3.04, QGSJET I -.1em I-03 and PYTHIA 8.145, are in good agreement with the data below 300 GeV but predict harder energy spectra than the data above 300 GeV. The results of these comparisons exhibited features similar to those for the previously reported data for $\sqrt{s}=$ 7 TeV collisions.

The transverse momentum ($p_\text{T}$) distribution for inclusive neutral pions in the very forward rapidity region has been measured, with the Large Hadron Collider forward detector (LHCf), in proton--lead collisions at nucleon-nucleon center-of-mass energies of $\sqrt{s_{NN}} = 5.02$TeV at the LHC. The $p_\text{T}$ spectra obtained in the rapidity range $-11.0 < y_\text{lab} < -8.9$ and $0 < p_\text{T} < 0.6$GeV (in the detector reference frame) show a strong suppression of the production of neutral pions after taking into account ultra-peripheral collisions. This leads to a nuclear modification factor value, relative to the interpolated $p_\text{T}$ spectra in proton-proton collisions at $\sqrt{s} = 5.02$TeV, of about 0.1--0.4. This value is compared with the predictions of several hadronic interaction Monte Carlo simulations.

The Electron-Ion Collider (EIC) is a cutting-edge accelerator facility that will study the nature of the "glue" that binds the building blocks of the visible matter in the universe. The proposed experiment will be realized at Brookhaven National Laboratory in approximately 10 years from now, with detector design and R&D currently ongoing. Notably, EIC is one of the first large-scale facilities to leverage Artificial Intelligence (AI) already starting from the design and R&D phases. The EIC Comprehensive Chromodynamics Experiment (ECCE) is a consortium that proposed a detector design based on a 1.5T solenoid. The EIC detector proposal review concluded that the ECCE design will serve as the reference design for an EIC detector. Herein we describe a comprehensive optimization of the ECCE tracker using AI. The work required a complex parametrization of the simulated detector system. Our approach dealt with an optimization problem in a multidimensional design space driven by multiple objectives that encode the detector performance, while satisfying several mechanical constraints. We describe our strategy and show results obtained for the ECCE tracking system. The AI-assisted design is agnostic to the simulation framework and can be extended to other sub-detectors or to a system of sub-detectors to further optimize the performance of the EIC detector.

The EIC Comprehensive Chromodynamics Experiment (ECCE) detector has been designed to address the full scope of the proposed Electron Ion Collider (EIC) physics program as presented by the National Academy of Science and provide a deeper understanding of the quark-gluon structure of matter. To accomplish this, the ECCE detector offers nearly acceptance and energy coverage along with excellent tracking and particle identification. The ECCE detector was designed to be built within the budget envelope set out by the EIC project while simultaneously managing cost and schedule risks. This detector concept has been selected to be the basis for the EIC project detector.

Gd2SiO5 (GSO) scintillator has very excellent radiation resistance, a fast decay time and a large light yield. Because of these features, GSO scintillator is a suitable material for high radiation environment experiments such as those encountered at high energy accelerators. The radiation hardness of GSO has been measured with Carbon ion beams at the Heavy Ion Medical Accelerator in Chiba (HIMAC). During two nights of irradiation the GSO received a total radiation dose of 7 × 105 Gy and no decrease of light yield was observed. On the other hand an increase of light yield by 25% was observed. The increase is proportional to the total dose, increasing at a rate of 0.025%/Gy and saturating at around 1 kGy. Recovery to the initial light yield was also observed during the day between two nights of radiation exposure. The recovery was observed to have a slow exponential time constant of approximately 1.5 × 104 seconds together with a faster component. In case of the LHCf experiment, a very forward region experiment on LHC (pseudo-rapidity η > 8.4), the irradiation dose is expected to be approximately 100 Gy for 10 nb−1 of data taking at (s)1/2 = 14TeV. The expected increase in light yield of less than a few percent will not affect the LHCf measurement.

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. It measures neutral particles emitted in the very forward region of the LHC p-p or p-N 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 varies from 70% to 80% above 500 GeV. The energy resolutions are about 40% and the position resolution is 0.1 to 1.3 mm depending 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.

The LHCf experiment aims to improve knowledge of forward neutral particle production spectra at the LHC energy which is relevant for the interpretation of air shower development of high energy cosmic rays. Two detectors, each composed of a pair of sampling and imaging calorimeters, have been installed at the forward region of IP1 to measure π0 energy spectra above 600 GeV. In this paper, we present a Monte Carlo study of the π0 measurements to be performed with one of the LHCf detectors for proton–proton collisions at s=14 TeV. In approximately 40 min of operation at luminosity 0.8×1029cm-2s-1 during the beam commissioning phase of LHC, about 1.5 × 104 π0 events are expected to be obtained at two transverse positions of the detector. The backgrounds from interactions of secondary particles with beam pipes and interactions of beam particles with residual gas in the beam pipes are expected to be less than 0.1% of the signal from π0s. We also discuss the capability of LHCf measurements to discriminate between the various hadron interaction models that are used for simulation of high energy air showers, such as DPMJET3.03, QGSJETII-03, SIBYLL2.1 and EPOS1.99.

To increase the radiation resistivity of the calorimeter, the LHCf group plans to replace its plastic scintillator with Gd2SiO5 (GSO) scintillator. In this report, we present the basic performance of very thin GSO scintillator bars that will replace the scintillating fibers employed as the position sensitive part of the current LHCf detector. The size of a bar is 1 mm × 1 mm × 40 mm. White acrylic paint was painted on one group of GSO bars and a second group was unpainted. After observing a clear peak of cosmic ray muons corresponding to 3 to 4 photoelectrons, a quantitative test was performed by using a 290 MeV/n carbon beam at HIMAC in Japan. The non-painted bars have less position dependence of light collection efficiency (effective attenuation length is about 140 mm) and less piece-to-piece variation. The unpainted bars show about 8% cross talk between adjacent bars which is larger than the painted ones. However, for estimating the center of a cascade shower inside the calorimeter, uniformity of light collection is more important than cross talk, so we have decided to use non-painted bars in the LHCf detector. A simulation of a 100 GeV electron injected in the center of the detector shows that position dependence and cross talk cause only a 0.04 mm shift of the shower centroid without any correction applied. This shows that these effects are relatively small compared to the uncertainty of the beam center position which was 1 mm for the LHCf experiments already performed at √s =7 TeV.

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 π0'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=900GeV and s=7TeV proton–proton collisions in 2009 and 2010. We present the first physics result, single photon energy spectra at s=7TeV 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.

Large Hadron Collider forward (LHCf) has successfully completed the operation during the LHC 2009–2010 period and the detectors were removed in July 2010. The event trigger, data analysis and background have been intensively studied in order to derive inclusive single photon and π 0 spectra. In this paper, the details of these intensive studies are described.

The LHCf experiment, optimized for the study of forward physics at LHC, completes its main physics program in this year 2015, with the proton-proton collisions at the energy of 13 TeV.LHCf gives important results on the study of neutral particles at extreme pseudo-rapidity, both for proton-proton and for proton-ion interactions.These results are an important reference for tuning the models of the hadronic interaction currently used for the simulation of the atmospheric showers induced by very high energy cosmic rays.The results of this analysis and the future perspective are presented in this paper.

The LHC-forward (LHCf) experiment, situated at the LHC accelerator, has measured neutral particles production in a very forward region (pseudo-rapidity > 8.4) in proton-proton and proton-lead collisions. The main purpose of the LHCf experiment is to test hadronic interaction models used in cosmic rays experiments to imulate cosmic rays induced air-showers in Earth’s atmosphere.

The LHC forward experiment (LHCf) is specifically designed for measurements of the very forward ($η$$&gt;$8.4) production cross sections of neutral pions and neutrons at Large Hadron Collider (LHC) at CERN. LHCf started data taking in December 2009, when the LHC started to provide stable collisions of protons at $\sqrt{s}$=900\,GeV. Since March 2010, LHC increased the collision energy up to $\sqrt{s}$=7\,TeV. By the time of the symposium, LHCf collected 113k events of high energy showers (corresponding to $\sim$7M inelastic collisions) at $\sqrt{s}$=900\,GeV and $\sim$100M showers ($\sim$14 nb$^{-1}$ of integrated luminosity) at $\sqrt{s}$=7\,TeV. Analysis results with the first limited sample of data demonstrate that LHCf will provide crucial data to improve the interaction models to understand very high-energy cosmic-ray air showers.

The LHCf experiment is one of the LHC forward experiments. The aim of LHCf is to provide critical calibration data of hadronic intraction models used in air shower simulations. The LHCf has completed the operations for p-p collisions with a collision energy of √s = 0.9 and 7 TeV p-p in 2010 and for p-Pb collisions with a collision energy per nucleon of √sNN = 5.02. The recent LHCf result of forward neutron energy spectra at 7 TeV p-p collision and forward π0 spectra at p-Pb collisions are presented in this paper.

The LHCf experiment is dedicated to the measurement of very forward particle production in the high energy hadron-hadron collisions at LHC, with the aim of improving the cosmic-ray air shower developments models. The detector has taken data in p-p collisions at different center of mass energies, from 900 GeV up to 7 TeV, and in p-Pb collisions at s=5.02 TeV. The results of forward production spectra of neutrons in p-p collisions and π0 in p-Pb collisions, compared with the models most widely used in the High Energy Cosmic Ray physics, are presented in this paper.

LHCf is an experiment designed to study the forward emission of neutral particles produced in proton-proton and proton-nucleus collisions at the LHC. The detectors consists of a pair of electromagnetic sampling calorimeters installed on both sides of the ATLAS interaction point IP1 at a distance of 140 m, covering the pseudorapidity range from 8.4 to infinity. The experiment has successfully measured the energy spectra of gamma rays, neutral pions and neutrons in p-p collisions at 0.9 TeV and 7 TeV, and of neutral pions in p-Pb collisions at 5.02 TeV and in p-p collisions at 2.76 TeV. The most recent data set has been acquired during a special physics run of p-p collisions at 13 TeV in June 2015 after the restart of the LHC. This set of measurements represent an useful contribution to the calibration and tuning of the hadronic interaction models used for the simulation of atmospheric showers induced by very-high energy cosmic rays, as the measured energy interval corresponds to the range 1014 - 1017 eV in the laboratory frame.

Measurements of normalized differential cross-sections of top quark pair ($t\bar t$) production are presented as a function of the mass, the transverse momentum and the rapidity of the $t\bar t$ system in proton-proton collisions at center-of-mass energies of $\sqrt{s}$ = 7 TeV and 8 TeV. The dataset corresponds to an integrated luminosity of 4.6 fb$^{-1}$ at 7 TeV and 20.2 fb$^{-1}$ at 8 TeV, recorded with the ATLAS detector at the Large Hadron Collider. Events with top quark pair signatures are selected in the dilepton final state, requiring exactly two charged leptons and at least two jets with at least one of the jets identified as likely to contain a $b$-hadron. The measured distributions are corrected for detector effects and selection efficiency to cross-sections at the parton level. The differential cross-sections are compared with different Monte Carlo generators and theoretical calculations of $t\bar t$ production. The results are consistent with the majority of predictions in a wide kinematic range.

The Large Hadron Collider forward (= LHCf) experiment has successfully finished the first phase of data taking at LHC √s = 0.9 and 7 TeV proton-proton collisions in 2010. As current status, we concentrate on analyzing the obtained data. As the first result, the energy spectra of photon measured by LHCf during = 7 TeV p-p collision has been published recently. Also the study of the upgraded version of LHCf detector for future = 14TeV run scenario is developed with the GSO scintillator. Another possible plan of p-A(nuclear) collision in LHC is also studied. In this paper, as the current status of the experiment, analyses, and works for foreseen detector upgrade are summarized.

The LHCf Collaboration has completed the first step of its scheduled physics program for the study of emission of neutral particles in the forward region of proton-proton (pp) interactions at LHC. Between 2009 and 2010 the LHCf experiment has successfully taken data at 900 GeV and 7TeV total energy in the center-of-mass frame of reference (CM). After a short presentation of the experimental apparatus, the results for the γ-ray spectrum at √s = 7TeV are presented in this paper.

In cosmic ray physics, the uncertainty of the hadron interaction model causes systematic errors of air shower simulations in high‐energy region. To solve the problem, the LHCf experiment measures energies and transverse momenta of neutral particles emitted in the forward region of 14 TeV p‐p collision at CERN LHC. Two LHCf detectors, consisting of sampling and imaging calorimeters, are installed at zero degree collision angle at + 140 m from the interaction point 1 (IP1). The energy resolution is confirmed as to be <5% and the position resolution <0.2 mm for gamma‐rays with energies from 100 GeV to 200 GeV by test beam results at the CERN SPS. Use of the Front Counter reduces the beam‐gas background by a factor 50.

LHCf measures the energy and transverse momentum of neutral particles produced in the forward region of the LHC interaction point. In high energy cosmic ray measurements, the results strongly depend on the hadron interaction model which is used in the air shower simulation. LHCf will take data at s = 0.9, 2.4, 7, 10 and 14 TeV collisions at LHC and provide crucial calibration points for the hadron interaction models.

A summary of recent results on top quark production at LHC and Tevatron are presented in this paper.The measurements of top quark production were performed in various energies ( √ s =1.96, 7, 8, 13 TeV) and initial states (p p and pp) by the ATLAS, CDF, CMS, DØ and LHCb experiments.The measured top quark pair production cross-section is in good agreement with the standard model predictions in each energy region.Differential cross-sections were also measured and compared with several theoretical predictions.Most of the higher order QCD models reproduce the experimental data well, while a slight discrepancy in a certain phase space such as higher top quark p T region is observed.Electroweak single top quark production was also measured and the results are consistent with theoretical predictions at the various energies.

The LHCf experiment is an unique dedicated experiment for measurement of very forward particle production relevant to cosmic-ray air shower developments. The LHCf measured the spectra for forward photons, neutral pions and neutrons at $\sqrt{s}$ = 7 TeV p–p collisions and the nuclear modification factor for forward neutral pions at $\sqrt{s}$ = 5 TeV p-Pb. No hadronic interaction models used in air shower developments of very high energy cosmic-rays is able to reproduce all LHCf data reasonably while some of models are able to reproduce LHCf data partially.

The LHCf experiment is an unique dedicated experiment for measurement of very forward particle production relevant to cosmic-ray air shower developments.The LHCf measured the spectra for forward photons, neutral pions and neutrons at √ s = 7 TeV p-p collisions and the nuclear modification factor for forward neutral pions at √ s = 5 TeV p-Pb.No hadronic interaction models used in air shower developments of very high energy cosmic-rays is able to reproduce all LHCf data reasonably while some of models are able to reproduce LHCf data partially.

The large centre-of-mass energy available at the Large Hadron Collider (LHC) allows for the copious production of top quark pairs in association with other final state particles at high transverse momenta.Several final state observables that are sensitive to additional radiation in top anti-top quark final states has been measured by the ATLAS experiment.The production of top quark pair in association with W and Z bosons or with a photon have been also measured.Analyses probing the top pair production with additional QCD radiation include the multiplicity of jets for various transverse momentum thresholds in the 13 TeV data.These measurements are compared to modern Monte Carlo generators based on NLO QCD matrix element or LO multi-leg matrix elements, and the results are consistent with the standard model predictions within the uncertainties.