First Measurements of Beam Backgrounds at SuperKEKB
P. M. Lewis, I. Jaegle, H. Nakayama, A. Aloisio, F. Ameli, M. Barrett, A. Beaulieu, L. Bosisio, P. Branchini, T. E. Browder, A. Budano, G. Cautero, C. Cecchi, Y… 展开作者
P. M. Lewis, I. Jaegle, H. Nakayama, A. Aloisio, F. Ameli, M. Barrett, A. Beaulieu, L. Bosisio, P. Branchini, T. E. Browder, A. Budano, G. Cautero, C. Cecchi, Y. -T. Chen, K. -N. Chu, D. Cinabro, P. Cristaudo, S. de Jong, R. de Sangro, G. Finocchiaro, J. Flanagan, Y. Funakoshi, M. Gabriel, R. Giordano, D. Giuressi, M. T. Hedges, N. Honkanen, H. Ikeda, T. Ishibashi, H. Kaji, K. Kanazawa, C. Kiesling, S. Koirala, P. Križan, C. La Licata, L. Lanceri, J. -J. Liau, F. -H. Lin, J. -C. Lin, Z. Liptak, S. Longo, E. Manoni, C. Marinas, K. Miyabayashi, E. Mulyani, A. Morita, M. Nakao, M. Nayak, Y. Ohnishi, A. Passeri, P. Poffenberger, M. Ritzert, J M. Roney, A. Rossi, T. Röder, R. M. Seddon, I. S. Seong, J. -G. Shiu, F. Simon, Y. Soloviev, Y. Suetsugu, M. Szalay, S. Terui, G. Tortone, S. E. Vahsen, N. van der Kolk, L. Vitale, M. Z. Wang, H. Windel, S. Yokoyama
The high design luminosity of the SuperKEKB electron-positron collider is expected to result in challenging levels of beam-induced backgrounds in the interaction region. Properly simulating and mitigating these backgrounds is critical to the success of the Belle~II experiment. We report on measurements performed with a suite of dedicated beam background detectors, collectively known as BEAST II, during the so-called Phase 1 commissioning run of SuperKEKB in 2016, which involved operation of both the high energy ring (HER) of 7 GeV electrons as well as the low energy ring (LER) of 4 GeV positrons. We describe the BEAST II detector systems, the simulation of beam backgrounds, and the measurements performed. The measurements include standard ones of dose rates versus accelerator conditions, and more novel investigations, such as bunch-by-bunch measurements of injection backgrounds and measurements sensitive to the energy spectrum and angular distribution of fast neutrons. We observe beam-gas, Touschek, beam-dust, and injection backgrounds. We do not observe significant synchrotron radiation, as expected. Measured LER beam-gas backgrounds and Touschek backgrounds in both rings are slightly elevated, on average three times larger than the levels predicted by simulation. HER beam-gas backgrounds are on on average two orders of magnitude larger than predicted. Systematic uncertainties and channel-to-channel variations are large, so that these excesses constitute only 1-2 sigma level effects. Neutron background rates are higher than predicted and should be studied further. We will measure the remaining beam background processes, due to colliding beams, in the imminent commissioning Phase 2. These backgrounds are expected to be the most critical for Belle II, to the point of necessitating replacement of detector components during the Phase 3 (full-luminosity) operation of SuperKEB.
Development of a Silicon-Based Ultra-Fast X-Ray Beam Size Monitor for SuperKEKB
University of Hawaii（夏威夷大学）；High Energy Accelerator Research Organization (KEK)（高能加速器研究机构）；Department of Physics, University of Tokyo（东京大学物理系）；The Graduate University for Advanced Studies (SOKENDAI)（综合研究大学院大学）；SLAC National Accelerator Laboratory（SLAC国家加速器实验室）；Graduate School of Science, Nagoya University（名古屋大学理学研究科）
We report on measurements of beam backgrounds during the first commissioning phase of the SuperKEKB collider in 2016, performed with the plastic scintillator and silicon photomultiplier-based CLAWS detector system. The sub-nanosecond time resolution and single particle detection capability of the sensors allow bunch-by-bunch measurements, enable CLAWS to perform a novel time resolved analysis of beam backgrounds, and make the system uniquely suited for the study of injection backgrounds. We present measurements of various aspects of regular beam background and injection backgrounds which inclu…
Anomaly Detection in Bunch Oscillations for Early Warning of Sudden Beam Loss at SuperKEKB
Marietta Blau Institute, Austrian Academy of Sciences（玛丽塔·布劳研究所，奥地利科学院）；University of Victoria（维多利亚大学）；High Energy Accelerator Research Organization (KEK)（高能加速器研究机构（KEK））；The Graduate University for Advanced Studies (SOKENDAI)（综合研究大学院大学（SOKENDAI））；Department of Physics, The University of Tokyo（东京大学物理系）
We present results from the first deployment of novel, high definition, compact gas Time Projection Chambers (TPCs) with pixel chip readout as part of the BEAST II beam background measurement project at SuperKEKB. The TPCs provide detailed 3D imaging of ionization from neutron-induced nuclear recoils in a helium and carbon dioxide target gas mixture at standard temperature and pressure. We find excellent electron background rejection, leading to background-free nuclear recoil measurements above 50 keVee, despite the extreme high-background environment. We measure an angular resolution better t…
The high design luminosity of the SuperKEKB electron-positron collider will result in challenging levels of beam-induced backgro\ unds in the interaction region. Understanding and mitigating these backgrounds is critical to the success of the Belle~II experi\ ment. We report on the first background measurements performed after roll-in of the Belle II detector, a period known as SuperKE\ KB Phase 2, utilizing both the BEAST II system of dedicated background detectors and the Belle II detector itself. We also repor\ t on first revisions to the background simulation made in response to our findin…
Gaseous time projection chambers (TPCs) with high readout segmentation are capable of reconstructing detailed 3D ionization distributions of nuclear recoils resulting from elastic neutron scattering. Using a system of six compact TPCs with pixel ASIC readout, filled with a 70:30 mixture of He:CO$_2$ gas, we analyze the first directional measurements of beam-induced neutron backgrounds in the tunnel regions surrounding the Belle II detector at the SuperKEKB $e^+e^-$ collider. With the use of 3D recoil tracking, we show that these TPCs are capable of maintaining nearly $100\%$ nuclear recoil pur…
The Belle-II VerteX Detector (VXD) is a 6 layers silicon tracker device that will cope with an unprecedented luminosity of 8 x 10^35 cm-2 s-1 achievable by the new SuperKEKB e+e- collider, now under commissioning at the KEK laboratory (Tsukuba, Japan). A radiation monitoring and beam abort system has been developed based on single-crystal s-CVD diamond sensors. The sensors will be placed in 20 key positions in the vicinity of the interaction region. The severe space limitations require a remote readout of the sensors. In this contribution we present the system design, along with the sensor cha…
The Belle II experiment will be at the forefront of indirect searches for non-Standard-Model physics using billions of heavy quarks and $τ$ leptons produced in high-intensity 10 GeV electron-positron collisions from the SuperKEKB collider. The intense beams needed to achieve the required precisions are associated with high beam-background radiation that may damage the inner detectors. A dedicated radiation-monitoring and beam-abort system, based on artificial diamond sensors, ensures protection and safe data taking conditions. I briefly outline the system and illustrate the operational experie…
The Belle II detector is currently under construction at the SuperKEKB electron-positron high-luminosity collider, that will provide an instantaneous luminosity 40 times higher than that of KEKB. There- fore the Belle-II VerteX Detector (VXD) will operate in a very harsh environment. A radiation monitoring and beam abort system is needed to safely operate the VXD detector in these conditions. This system is based on 20 single crystal CVD diamond sensors placed in 20 key positions in the vicinity of the VXD and interaction region. In this contribution we describe the system design and we presen…
Using the Belle detector we study the characteristics of beam collisions at the KEKB 3.5 GeV $e^+$ on 8 GeV $e^-$ asymmetric energy collider. We investigate the collision timing {\tip} and its $z$-coordinate along the beam axis {\zip} as a function of the position of the colliding bunch in a beam train. The various {\tip} and {\zip} behaviors observed by Belle are attributed to beam loading effects in the radio frequency cavities that accelerate the beams with a beam abort gap. We report these results in detail and discuss the prospects for the SuperKEKB collider.
The Belle II experiment has been preparing for its first e+ e- collisions, scheduled in April 2018. With a target luminosity 40 times greater than the Belle experiment, the goal of Belle II is to open the door to a panorama of measurements in heavy flavour physics and much more. The initial beams and the commissioning of the SuperKEKB collider took place earlier in 2016. After completing most of the detector assembly and performing test runs with cosmic rays, the experiment is ready for initial collisions. Soon after in early 2019, data collection with the full Belle II detector will commence …
The Belle II detector at the SuperKEKB accelerator has a level 1 trigger implemented in field-programmable gate arrays. Due to the high luminosity of the beam, a trigger that effectively rejects beam induced background is required. A three dimensional tracking algorithm for the level 1 trigger that uses the Belle II central drift chamber detector response is being developed to reduce the recorded beam background while having a high efficiency for physics of interest. In this paper, we describe the three dimensional track trigger that finds and fits track parameters which we developed.
Artificially-grown diamond crystals have unique properties that make them suitable as solid-state particle detectors and dosimeters in high-radiation environments. We have been using sensors based on single-crystal diamond grown by chemical vapour deposition for dosimetry and beam-loss monitoring at the SuperKEKB collider. Here we describe the assembly and the suite of test and calibration procedures adopted to characterise the diamond-based detectors of this monitoring system. We report the results obtained on 28 detectors and assess the stability and uniformity of response of these devices.
We designed, constructed and have been operating a system based on single-crystal synthetic diamond sensors, to monitor the beam losses at the interaction region of the SuperKEKB asymmetric-energy electron-positron collider. The system records the radiation dose-rates in positions close to the inner detectors of the Belle II experiment, and protects both the detector and accelerator components against destructive beam losses, by participating in the beam-abort system. It also provides complementary information for the dedicated studies of beam-related backgrounds. We describe the performance o…
Beam commissioning of the SuperKEKB collider began in 2016. The Beam Exorcism for A STable experiment II (BEAST II) project is particularly designed to measure the beam backgrounds around the interaction point of the SuperKEKB collider for the Belle II experiment. We develop a system using bismuth germanium oxide (BGO) crystals with optical fibers connecting to a multianode photomultiplier tube (MAPMT) and a field-programmable gate array (FPGA) embedded readout board for monitoring the real-time beam backgrounds in BEAST II. The overall radiation sensitivity of this system is estimated to be $…
The Belle II experiment at the Super B factory SuperKEKB, an asymmetric $e^+e^-$ collider located in Tsukuba, Japan, is tailored to perform precision B physics measurements. The centre of mass energy of the collisions is equal to the rest mass of the $Υ(4S)$ resonance of $m_{Υ(4S)} = 10.58\,\rm GeV$. A high vertex resolution is essential for measuring the decay vertices of B mesons. Typical momenta of the decay products are ranging from a few tens of MeV to a few GeV and multiple scattering has a significant impact on the vertex resolution. The VerteX Detector (VXD) for Belle II is therefore d…
The Silicon Detector (SiD) is one of the detector concepts for the International Linear Collider (ILC), which is proposed to be built in Japan. Since the decision to reduce the center-of-mass energy for the first stage of the ILC to 250 GeV, numerous efforts are ongoing to evaluate the possible physics program and the change in the detector background. It was found that changing the beam parameters would increase the luminosity and therefore further strengthen the physics outcome. On the downside, the new beam parameters lead to an increase in the detector background arising from beam-beam int…
Since the start of data taking in spring 2019 at the SuperKEKB collider (KEK, Japan) the Belle II Silicon Vertex Detector (SVD) has been operating reliably and with high efficiency, while providing high quality data: high signal-to-noise ratio, greater than 99% hit efficiency, and precise spatial resolution. These attributes, combined with stability over time, result in good tracking efficiency. Currently the occupancy, dominated by beam-background hits, is quite low (about 0.5% in the innermost layer), causing no problems to the SVD data reconstruction. In view of the operation at higher lumi…
At the ILC machine induced backgrounds, mainly electron-positron pairs from beamstrahlung, will be the most important source of unwanted interactions. Methods of generating, simulating and imposing pair-background on physics events are presented and influence of this background on ILD reconstruction is reviewed. Effects of the background on various ILD detectors are shown for nominal beam parameters and for SB09 reduced beam parameter set and an example of a physics analysis performed with overlayed pair background is given.
Some high-energy experiments have suffered from synchrotron-radiation background. As a measure, we have developed a new calculation method of synchrotron radiation based on a real beam orbit, aiming at quantitative estimations and the construction of a possible alarm system for the background. An explanation and a demonstration of our method are given.
The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) aims to make a unique measurement of neutron yield from neutrino-nucleus interactions and to perform R&D for the next generation of water-based neutrino detectors. In this paper, we characterize beam-induced neutron backgrounds in the experimental hall at Fermi National Accelerator Laboratory. It is shown that the background levels are sufficiently low to allow the next stage of the experiment to proceed. These measurements are relevant to other Booster Neutrino Beam (BNB) experiments located adjacent to ANNIE Hall, where dirt neu…
The dense beams used at CLIC to achieve a high luminosity will cause a large amount of background particles through beam-beam interactions. Generator level studies with GuineaPig and full detector simulation studies with an ILD based CLIC detector have been performed to evaluate the amount of beam-beam background hitting the vertex detector.
Future collider detectors at muon colliders will be bombarded by Beam-Induced Backgrounds (BIB) due to the in-flight muon decays from the beam line. These backgrounds can inhibit the ability of the detector and subsequent data analysis to successfully reconstruct collision products. We explore methods for geometrically reducing these effects for use in the readout, triggering, and data analysis of future experiments. Studies are performed for a collision energy of 1.5~TeV, and a detector with a tungsten nozzle designed to block the majority of the BIB. In this context, detector strategies are …
With a multi-stage collimation system and magnetic iron spoilers in the tunnel, the background particle fluxes on the ILC detector can be substantially reduced. At the same time, beam-halo interactions with collimators and protective masks in the beam delivery system create fluxes of muons and other secondary particles which can still exceed the tolerable levels for some of the ILC sub-detectors. Results of modeling of such backgrounds in comparison to those from the e+ e- interactions are presented in this paper for the SiD detector.
The Belle II experiment at KEK in Japan has started real data taking from April 2018 to probe a New Physics beyond the Standard Model by measuring CP violation precisely and rare weak decays of heavy quark and lepton. The experiment is performed at the high luminosity SuperKEKB e^+ e^- collider with 80 x 10^34 cm^-2 s^-1 as an ultimate instantaneous luminosity. In order to develop and test an appropriate trigger algorithm under much higher luminosity and beam background environment than previous KEKB collider, a detail simulation study of the Belle II calorimeter trigger system is very crucial…
This article reports the first operation of a double-sided CMOS pixelated ladder in a collider experiment, namely in the inner tracker volume of the Belle II experiment during the Phase 2 run of the SuperKEKB collider. Design and integration of the detector system in the experiment interaction region is first described. The two modules operated almost continuously during slightly more than four months, recording data for the monitoring of the hit rate close to beams. Details of the off-line data analysis are provided and a method to estimate particle momentum from the 2 hits measured per cross…
This note discusses methods of particle reconstruction in the forward region detectors of future e+e- linear colliders such as ILC or CLIC. At the nominal luminosity the innermost electromagnetic calorimeters undergo high particle fluxes from the beam-induced background. In this prospect, different methods of the background simulation and signal electron reconstruction are described.
Ion chambers used to monitor the secondary hadron and tertiary muon beam in the NuMI neutrino beamline will be exposed to background particles, including low energy neutrons produced in the beam dump. To understand these backgrounds, we have studied Helium- and Argon-filled ionization chambers exposed to intense neutron fluxes from PuBe neutron sources ($E_n=1-10$ MeV). The sources emit about 10$^8$ neutrons per second. The number of ion pairs in the chamber gas volume per incident neutron is derived. While limited in precision because of a large gamma ray background from the PuBe sources, our…
The SiD concept is one of two proposed detectors to be mounted at the interaction region of the International Linear Collider (ILC). A substantial ILC background arises from low transverse momentum $\mathrm{e}^{+}\mathrm{e}^{-}$ pairs created by the interaction of the colliding beams' electromagnetic fields. In order to provide hermeticity and sensitivity to beam targeting parameters, a forward Beamline Calorimeter (BeamCal) is being designed that will provide coverage down to 5 mrad from the outgoing beam trajectory, and intercept the majority of this pair background. Using the SiD simulation…
The Belle II experiment, located at the SuperKEKB collider at the high-energy research facility KEK in Tsukuba, Japan, started operation in 2018. Compared to the predecessor experiment Belle, Belle II plans to increase the peak luminosity by a factor of about 40, by employing nano-beam technology in the interaction region. In particular the new, innermost sub-detector of Belle II - the Pixel Vertex Detector (PXD) - is in close proximity to the interaction point. This allows for the detection of particles, which do not leave a signal in the outer sub-detectors. Among these, Highly Ionizing Part…
The beams at the ILC produce electron positron pairs due to beam-beam interactions. This note presents for the first time a study of these processes in a detailed simulation, which shows that these pair background particles appear at angles that extend to the inner layers of the detector. The full data set of pairs produced in one bunch crossing was used to calculate the helix tracks, which the particles form in the solenoid field of the SiD detector. The results suggest to further study the reduction of the beam pipe radius and therefore to either add another SiD vertex detector layer, or red…
Monitoring the tagging efficiency of the Low-Energy Muon beamline through background analysis: Insights into the long-term performance of ultrathin carbon foils
PSI Center for Neutron and Muon Sciences CNM（瑞士保罗谢勒研究所中子与μ子科学中心）；Department of Physics, University of Basel（巴塞尔大学物理系）
The Belle detector operated at KEKb B-factory in 1999-2010 was one of the most remarkable experiments in the field of elementary particle physics of the last decades. The Belle successor, Belle II collaboration, is aimed to operate the Belle II detector at SuperKEKb factory at 40 times higher luminosity. Increased luminosity imposes new requirements on the detector elements: they have to survive at higher radiation levels, to operate at higher loads and at higher backgrounds. The Belle K_L and muon system based on the resistive plate chambers (RPC) technology worked well during all data taking…
In this talk recent simulation results on the single high energy electron reconstruction with the Beam Calorimeter for the ILD detector are presented. Guinea Pig is used to generate the e+e- pair background and GEANT4 for the simulation of electron showers in the calorimeter. An algorithm was developed for the sHEe reconstruction on top of the large e+e- background. The efficiency of the sHEe reconstruction is estimated for the nominal and SB-2009 ILC beam parameters.
A new Beam Halo Monitor (BHM) detector system has been installed in the CMS cavern to measure the machine-induced background (MIB) from the LHC. This background originates from interactions of the LHC beam halo with the final set of collimators before the CMS experiment and from beam gas interactions. The BHM detector uses the directional nature of Cherenkov radiation and event timing to select particles coming from the direction of the beam and to suppress those originating from the interaction point. It consists of 40 quartz rods, placed on each side of the CMS detector, coupled to UV sensit…
The beam calorimeter, located in the very forward and backward region of the next generation electron-positron linear accelerator, will be an important apparatus to search for or identify new particles beyond Standard Model. One of its key design issues is to estimate the radiation dosage due to beam related backgrounds. We used the geant-based package, Jupiter, for the proposed GLD detector in this study. The dosage received per year for the inner most ring will be around 10 Mrad. An algorithm for electron identification with beam calorimeter under nominal background condition is developed an…
The KOTO experiment is a particle physics experiment located in J-PARC, Japan, aiming to explore physics beyond the Standard Model by measuring the branching ratio of the $K_L\rightarrowπ^{0}ν\barν$ decay. This decay has not yet been observed. The branching ratio predicted by the Standard Model of $(3.0\pm0.3)\times10^{-11}$ and the current experimental upper limit established by KEK E391a is $2.6\times10^{-8}$. The signal of $K_L\rightarrowπ^{0}ν\barν$ decay has the signature of two photons on the calorimeter with no signal on the veto detectors. It also has a large transverse momentum due to…
The long (3ms) proton pulse of the European Spallation Source (ESS) gives rise to unique and potentially high backgrounds for the instrument suite. In such a source an instrument capabilities will be limited by it's Signal to Noise (S/N) ratio. The instruments with a direct view of the moderator, which do not use a bender to help mitigate the fast neutron background, are the most challenging. For these beam lines we propose the innovative shielding of placing blocks of material directly into the guide system, which allow a minimum attenuation of the cold and thermal fluxes relative to the back…
In the future neutrino experiments, a beta-beam, which can produce pure electron neutrino beam, is expected to achive precise measurement of the neutrino oscillation parameters. In the $ν_μ$ appearance measurement of a beta-beam, a detector does not need to identify particle charge and thus, a water Cherecov detector will be a candidate for the far detector. In this paper, we study the expected signal detection efficiencies and background at the proposed beta beam facilities with the water Cherenkov detector. In the estimation, we use the current simulation and analysis tools developed for the…
In dark photon search experiments with electron beam-dumps, it is difficult to access the smaller dark photon life-time region of phase space due to enormous backgrounds from low-energy particles emerging from the target. In order to reduce the background, a thick beam-dump target is usually necessary. We propose to detect the Cherenkov radiation in gas due to ultra-relativistic electron and positron from dark photon decay. The secondary particles emerging from the beam dump have very little chance to produce such Cherenkov radiation in gas. Making use of the direction of the Cherenkov radiati…
Incoherent background can create an intrinsic problem for standard small angle neutron scattering measurements. Biological samples contain hydrogen which is a strong incoherent scatterer thus creating an intrinsic source of background that makes determination of the coherent scattering parameters difficult in special situations. This can especially be true for the Q-range from around 0.1-0.5 Å-1 where improper knowledge of the background level can lead to ambiguity in determination of the samples structure parameters. Polarization analysis is a way of removing this ambiguity by allowing one to…
We present a new experimental method for measuring the process of Coherent Elastic Neutrino Nucleus Scattering (CENNS). This method uses a detector situated transverse to a high energy neutrino beam production target. This detector would be sensitive to the low energy neutrinos arising from pion decays-at-rest in the target. We discuss the physics motivation for making this measurement and outline the predicted backgrounds and sensitivities using this approach. We report a measurement of neutron backgrounds as found in an off-axis surface location of the Fermilab Booster Neutrino Beam (BNB) ta…
To suppress the muon background arising from the Beam Delivery System (BDS) of the International Linear Collider (ILC), and to hinder it from reaching the interaction region, two different shielding scenarios are under discussion: five cylindrical muon spoilers with or without an additional magnetized shielding wall. Due to cost and safety issues, the scenario preferred by the Machine-Detector-Interface (MDI) group is to omit the shielding wall, although omitting it also has disadvantages. To support the decision making for the muon shielding, the impact of the muons from the two different shi…
The hit response of silicon vertex and tracking detectors to muon collider beam background and results of a study of hit reducing techniques are presented. The background caused by decays of the 750 GeV/c m+ and m- beams was simulated using the MARS15 program, which included the infrastructure of the beam line elements near the detector and the 10 degree nozzles that shield the detector from this background. The ILCRoot framework, along with the Geant4 program, was used to simulate the hit response of the silicon vertex and tracker detectors to the muon decay background remaining after the shi…
The relevant interaction energies for astrophysical radiative capture reactions are very low, much below the repulsive Coulomb barrier. This leads to low cross sections, low counting rates in $γ$-ray detectors, and therefore the need to perform such experiments at ion accelerators placed in underground settings, shielded from cosmic rays. Here, the feasibility of such experiments in the new shallow-underground accelerator laboratory in tunnels VIII and IX of the Felsenkeller site in Dresden, Germany, is evaluated. To this end, the no-beam background in three different types of germanium detect…
The ATF2 project aims at demonstrating the strong vertical electron beam focusing capability, down to the few tens of nanometers level, of a down scale prototype of the final focus system of the next generation of e+e- machines. ATF2 offers opportunities to check in a real accelerator environment case for the performances of the beam transport and background generation code, used in the simulation of the future e+e- machines, BDSIM, and for the performances of its underneath particle-matter simulation code, Geant4.
Proton radiography has proved increasingly successful as a diagnostic for electric and magnetic fields in high energy density physics experiments. Most experiments use target-normal-sheath-acceleration sources with a wide energy range in the proton beam, as the velocity spread can help differentiate between electric and magnetic fields and provide time histories in a single shot. However, in magnetised plasma experiments with strong background fields, the broadband proton spectrum leads to velocity-spread-dependent displacement of the beam and significant blurring of the radiograph. We describ…
