Colliding Beam Experiments Research Articles

R&D status of FARICH option for PID

The Super Charm-Tau Factory project is a future electron–positron colliding beam experiment with unprecedented high luminosity of 10[Formula: see text][Formula: see text]cm[Formula: see text][Formula: see text]s[Formula: see text] at the center of mass energy range from 3 to 7[Formula: see text]GeV. To perform the broad physics program, the high-performance universal detector is proposed. One of the main detector subsystems is the FARICH (Focusing Aerogel RICH) detector. The proposed FARICH scheme combined with abilities of tracking system will provide the excellent [Formula: see text]-separation for the whole operation momentum range and [Formula: see text]-separation up to momentum of 1.5[Formula: see text]GeV/c. In 2023 two multilayer focusing aerogel samples with record overall sizes [Formula: see text][Formula: see text]mm were produced in Novosibirsk. The results of the beam tests of these aerogel samples and comparison with simulation are presented. Conceptual design and some technical issues of the dedicated particle identification system based on FARICH technique are discussed as well.

Design of the CMS High Granularity Calorimeter trigger primitive generator system

The High Luminosity phase of the LHC (HL-LHC) is planned to begin data taking in 2029, with the instantaneous luminosity expected to increase to 4 times its current value and the average number of particle interactions per bunch crossing increasing by approximately 3.5 times its current value. The current endcap calorimeters in the CMS detector will be replaced by a novel high granularity calorimeter (HGCAL) that will have fine segmentation in both the transverse and longitudinal directions and will be the first such calorimeter specifically optimised for particle flow reconstruction to operate at a colliding-beam experiment. The Level 1 trigger of the CMS experiment will combine the calorimeter data with tracking information to allow particle-flow techniques to be used. The high granularity of the calorimeter leads to about six million readout channels in total, concentrated in one million trigger cells, sampled for the L1 trigger at a rate of 40 MHz. The trigger data volumes will be an order of magnitude above those currently handled in CMS, posing significant challenges for data manipulation and processing. In addition, the trigger algorithms must be able to efficiently reject the huge background rate in the forward region of the detector due to the high pileup environment. The status of the HGCAL trigger architecture and design, as well as the algorithms developed in order to tackled these major issues, is presented here. The data flow is described from the formation and preselection of trigger cells on detector to the generation of two types of trigger primitives off detector, projective towers of energy in the (η, ϕ) plane and three-dimensional clusters of particles. Particle flow will use these 3D clusters, and their formation is described and followed by recent developments in the optimization of their transverse size.

Booster free from spin resonance for future 100-km-scale circular e+e− colliders

Acceleration of polarized electron~(positron) beams in a booster synchrotron may suffer from depolarization due to crossings of many spin depolarization resonances, which could limit its applications. We have studied the spin depolarization resonance structure of a 100~km scale booster lattice of the Circular Electron Positron Collider~(CEPC). The lattice has 8 arc regions with hundreds of FODO cells, interleaved with straight sections, which leads to a high periodicity. Our analysis shows the contributions to the strength of intrinsic and imperfection spin resonances add up coherently near the super strong resonances beyond 120 GeV, but mostly cancel out and result in generally weak resonance strengths at lower beam energies. Detailed simulations confirm that beam polarization can be mostly maintained in the fast acceleration to 45.6 GeV and 80 GeV, but severe depolarization may occur at even higher energies. This study suggests the possibility of acceleration of polarized electron~(positron) beams to ultra-high beam energies without the help of Siberian snakes, and supports injecting highly polarized beams into the collider rings as an attractive solution for resonant depolarization measurements and longitudinal polarized colliding beam experiments for future 100~km scale circular e$^{+}$e$^{-}$ colliders.

Studies of the low voltage power supply for a highly segmented fast detector

The experiments at the Large Hadron Collider are upgrading their detectors for the coming High Luminosity run. Powering the on board electronics of the highly segmented tracking detectors is a challenge because of the stringent requirements on location, space constraint, fine segmentation, radiation and magnetic field tolerance, thermal loss, etc. Similar issues will be relevant for the future colliding beam experiments, also. This paper reports early studies of the Low Voltage Power Supply for the upgrade of the Outer Tracker detector of the Compact Muon Solenoid experiment. The proposed power chain uses point of load DC-DC converters. The studies, with simulations and experimental measurements, have identified a number of critical issues related to the voltages and currents of the DC-DC converters under different operating conditions. A few constraints on the design of such a system have been identified and in some cases remedial measures to circumvent such constraints have been suggested.

Heavy ion collider NICA at JINR

Main scientific goal of the NICA/MPD project (Nuclotron-based Ion Collider fAcility/ Multi Purpose Detector) under construction at JINR (Dubna) is exploration of the phase diagram of strongly interacting matter in the region of high compression. The planned experimental program includes studies of possible signs of the phase transitions and critical phenomena in heavy ion (up to Au) collisions at the center-of-mass energies up to 11 GeV/u. The collider experiment provides optimum conditions for efficient energy scan measurements. Attainment of the required average luminosity of the order of 1027 cm-2·s-1 for such physics experiment faces several accelerator physics and technology challenges. Contrary to high energy colliders, the luminosity of NICA case will be mostly limited by the Laslett tune shift, while the beam-beam tune shift parameter will be negligibly small. Flexible operational procedures for the beam storage and short bunch formation have been developed to provide maximum peak luminosity over wide energy range. Beam cooling is critical to counteract luminosity decay due to intra-beam scattering. NICA collider design addresses these issues and satisfies all the requirements for the colliding beams experiments.

Belle II electromagnetic calorimeter and its performance during early SuperKEKB operation

The Belle II experiment at the SuperKEKB accelerator is the new-generation intensity frontier electron-positron colliding beam experiment. The electromagnetic calorimeter consisting of 8736 CsI(Tl) crystals with their PIN-photodiode readout, has been inherited from the Belle experiment. In order to achieve high rate capability and immunity against beam background, the electronics has been upgraded to feature waveform sampling readout to provide not only energy deposition but also timing for each crystal hit. Design and construction of the upgraded electronics are reviewed and the performance in the early Belle II physics runs is reported. We also present the first application of calorimeter pulse shape discrimination at a B-Factory experiment. This novel technique, enabled by the new waveform sampling electronics, allows for discrimination between electromagnetic and hadronic showers, leading to significant improvements in kaon-long vs. photon separation and charged particle identification.

Concepts and design of the CMS high granularity calorimeter Level 1 trigger

The CMS collaboration has chosen a novel high granularity calorimeter for the endcap regions as part of its planned upgrade for the high luminosity LHC. The calorimeter will have fine segmentation in both the transverse and longitudinal directions and will be the first such calorimeter specifically optimised for particle-flow reconstruction to operate at a colliding-beam experiment. The calorimeter data will form part of the Level 1 trigger of the CMS experiment and, together with tracking information that will also be available at this level, should allow particle-flow techniques to be used as part of this trigger. The trigger has tight contraints on latency and rate, and will need to be implemented in hardware. The high granularity results in around six million readout channels in total, a million of which are also used as part of the Level 1 trigger, presenting a significant challenge in terms of data manipulation and processing for the trigger system. The trigger data volumes will be an order of magnitude above those currently handled at CMS. In addition, the high luminosity will result in an average of 140 (or more) interactions per bunch crossing that give a huge background rate in the forward region and these will need to be efficiently rejected by the trigger algorithms. Furthermore, reconstruction of the particle clusters to be used for particle flow in events with high hit rates is also a complex computational problem for the trigger. The status of the trigger architecture and design, as well as the concepts for the algorithms needed in order to tackle these major issues, will be presented.

Investigation of Cherenkov radiation component in LYSO(Ce) crystals

The fast scintillation crystals such as pure CsI or LYSO(Ce) today are considered for timing measurements in future colliding beam experiments. The aim of such counters is to determine time of particles arrival with accuracy better than 100 ps. The work is devoted to investigation of influence of Cherenkov radiation on the time resolution of the detectors based on LYSO(Ce) crystals. The results of MC simulation and beam test are presented.

Experimental Studies of the Production of π0-Mesons and η-Mesons in U + U Interactions at an Energy of 192 GeV

Studies of collisions between ultrarelativistic heavy nuclei at the Relativistic Heavy Ion Collider (RHIC) led to the discovery of a qualitatively new state of matter (strongly coupled quark–gluon plasma), in which quarks and gluons are not bound inside hadrons, but move freely within the volume of the created medium. The U + U collision system with an energy of 192 GeV at the RHIC is the heaviest system of colliding nuclei used in colliding beam experiments and allows us to obtain the highest energy density among systems of ultrarelativistic colliding nuclei. The results are presented from measuring factors of the nuclear modification of π0- and η-mesons in (U + U) collisions at an energy of 192 GeV.

The Super C-τ Factory particle identification system options

The Super C-τ (SCT) Factory at Novosibirsk is a project of new colliding beam experiment proposed in Budker Institute of Nuclear Physics. Electron-positron collider based on Crab-Waist technique for operation energy range 2–5 GeV in center of mass is suggested. The luminosity up to 1035cm−1s−1 (in 100 times higher than in operated today experiments in this energy region) is expected. To perform broad experimental program of the project successfully the excellent particle identification (PID) system is needed. A number of options are under consideration. Three of them are described in the paper: Focusing Aerogel RICH (FARICH) detector, threshold Cherenkov counters based on ASHIPH (Aerogel SHifter PHotomultiplier) technique with 6000 litres of aerogel of two refractive indexes and time-of-flight counters with TOP (Time of Propagation) approach with time resolution better than 30 ps. Comparison of PID capabilities with help of parametric simulation is given.

Concepts and design of the CMS high granularity calorimeter Level-1 trigger

The CMS experiment has chosen a novel high granularity calorimeter for the forward region as part of its planned upgrade for the high luminosity LHC. The calorimeter will have a fine segmentation in both the transverse and longitudinal directions and will be the first such calorimeter specifically optimised for particle flow reconstruction to operate at a colliding beam experiment. The high granularity results in around six million readout channels in total and so presents a significant challenge in terms of data manipulation and processing for the trigger; the trigger data volumes will be an order of magnitude above those currently handled at CMS. In addition, the high luminosity will result in an average of 140 to 200 interactions per bunch crossing, giving a huge background rate in the forward region that needs to be efficiently reduced by the trigger algorithms. Efficient data reduction and reconstruction algorithms making use of the fine segmentation of the detector have been simulated and evaluated. They provide an increase of the trigger rates with the luminosity significantly smaller than would be expected with the current trigger system.

Challenges of Particle Flow reconstruction in the CMS High-Granularity Calorimeter at the High-Luminosity LHC

The challenges of the High-Luminosity LHC (HL-LHC) are driven by the large number of overlapping proton-proton collisions (pileup) in each bunch-crossing and the extreme radiation dose to detectors at high pseudorapidity. To overcome this challenge CMS is developing an endcap electromagnetic+hadronic sampling calorimeter employing silicon sensors in the electromagnetic and front hadronic sections, comprising over 6 million channels, and highly-segmented plastic scintillators in the rear part of the hadronic section. This High- Granularity Calorimeter (HGCAL) will be the first of its kind used in a colliding beam experiment. Clustering deposits of energy over many cells and layers is a complex and challenging computational task, particularly in the high-pileup environment of HL-LHC. Baseline detector performance results are presented for electromagnetic and hadronic objects, and studies demonstrating the advantages of fine longitudinal and transverse segmentation are explored.

The ELISe experiment, potential paths towards its realization

In this paper the opportunities and prerequisites for carrying out electron scattering experiments off unstable beams for the first time will be outlined. A colliding beam experiment with intersecting electron and RIBs will be described, which allows making the best uses of the precious unstable nuclei for elastic and inelastic scattering using a pure electromagnetic probe. The experiment could be already realized within the modularized start version of the FAIR facility which is currently being constructed.

Аэрогелевые черенковские детекторы в экспериментах на встречных пучках

Аэрогелевые черенковские детекторы в экспериментах на встречных пучках

Impact of 3D polarization profiles on spin-dependent measurements in colliding beam experiments

We derive the effect of 3-dimensional polarization profiles on the measured polarization in polarimeters, as well as the observed polarization and the polarization-weighted luminosity (figure of merit) in single and double spin measurements in colliding beam experiments.

Impact of three-dimensional polarization profiles on spin-dependent measurements in colliding beam experiments

We derive the effect of 3-dimensional polarization profiles on the measured polarization in polarimeters, as well as the observed polarization and the polarization-weighted luminosity (figure of merit) in single and double spin measurements in colliding beam experiments. Applications to RHIC are discussed.

Imaging Calorimeter: What Have We Learned So Far

Abstract Particle Flow Algorithms (PFAs) have been applied to existing detectors to improve the measurement of hadronic jets in colliding beam experiments. For future experiments, such as a TeV lepton collider, detector concepts optimized for the application of PFAs are being developed. These concepts require so-called imaging calorimeters, with unprecedented granularity. We will review the various recent developments of such highly granular calorimeters.

Absolute luminosity measurements with the LHCb detector at the LHC

Absolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. Using data taken in 2010, LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC with a centre-of-mass energy of 7 TeV. In addition to the classic ``van der Meer scan'' method a novel technique has been developed which makes use of direct imaging of the individual beams using beam-gas and beam-beam interactions. This beam imaging method is made possible by the high resolution of the LHCb vertex detector and the close proximity of the detector to the beams, and allows beam parameters such as positions, angles and widths to be determined. The results of the two methods have comparable precision and are in good agreement. Combining the two methods, an overal precision of 3.5% in the absolute luminosity determination is reached. The techniques used to transport the absolute luminosity calibration to the full 2010 data-taking period are presented.

Collider, direct and indirect detection of supersymmetric dark matter

We present an overview of supersymmetry (SUSY) searches, both at collider experiments and via searches for dark matter (DM). We focus on three DM possibilities in the SUSY context: the thermally produced neutralino, a mixture of axion and axino, and the gravitino, and compare and contrast signals that may be expected at colliders, in direct detection (DD) experiments searching of DM relics left over from the Big Bang, and indirect detection (ID) experiments designed to detect the products of DM annihilations within the solar interior or galactic halo. Detection of DM particles using multiple strategies provides complementary information that may shed light on the new physics associated with the DM sector. In contrast to the minimal supergravity (mSUGRA) model where the measured cold DM relic density restricts us to special regions mostly on the edge of the m0–m1/2 plane, the entire parameter plane becomes allowed if the universality assumption is relaxed in models with just one additional parameter. Then, thermally produced neutralinos with a well-tempered mix of wino, bino and higgsino components, or with a mass adjusted so that their annihilation in the early Universe is Higgs-resonance-enhanced, can be the DM. Well-tempered neutralinos typically yield heightened rates for DD and ID experiments compared with generic predictions from mSUGRA. If instead DM consists of axinos (possibly together with axions) or gravitinos, then there exists the possibility of detection of quasi-stable next-to-lightest SUSY particles at colliding beam experiments, with especially striking consequences if the next-lightest-supersymmetric-particle (NLSP) is charged, but no DD or ID detection. The exception for mixed axion/axino DM is that DD of axions may be possible.

Mathematical modeling of non-scalar meson resonances

The mathematical form describing the frequency response of current in a series, inductor-resistor-capacitor (LRC) resonant circuit is employed as the basis for representing the mass distributions of a number of non-scalar mesons arising in high-energy colliding beam experiments. Unlike “one-at-a-time” representations, such as Lorentz Amplitudes, the model put forth below serves to link a series of from four to seven mesons via one function of mass and spin. Three such series of non-scalar mesons are investigated, from which investigation it is inferred that one of the speculative X(2080) mesons should likely be designated as . In addition, and interestingly enough, the fifth and sixth elements in another series bear a strong resemblance each to two formerly listed as speculative meson resonances, the ρ5(2350) and the f6(2510), respectively, neither of which is currently listed by the Particle Data Group. Finally, it is suggested that X(2750) should be designated as ρ7(2750).