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At the CERN Large Hadron Collider (LHC), absolute luminosity calibrations obtained by the van der Meer ( vdM ) method are affected by the mutual electromagnetic interaction of the two beams. In the last few years, increasingly stringent, physics-driven requirements on the accuracy of the absolute luminosity scale, combined with the unparalleled precision of the luminosity measurements achieved by the LHC experiments, motivated comprehensive simulation studies to accurately model beam–beam effects and provide simulation-based corrections to vdM -based luminosity calibrations. This paper reports the first attempt at an experimental validation of that model, in dedicated accelerator measurements under controlled conditions, of the predicted impact of beam-beam effects on the luminosity measured at the LHC under luminosity-calibration conditions. This is the first measurement of beam-beam interaction effects on luminosity at the LHC. The results show good agreement with the predictions of multiparticle simulations, and justify the recently proposed strategy for correcting beam-beam biases on absolute luminosity calibrations at hadron colliders. This marks a critical step forward in precise luminosity calibration for past, current, and future datasets, including the High-Luminosity Large Hadron Collider era.

A photoinjector, PHIN (PHotoINjector), has been realized at CERN by a joint effort of several institutes within the European Coordinated Accelerator Research in Europe program. The test facility has been installed and commissioned at CERN with the aim to demonstrate the beam parameters needed for the CLIC Test Facility 3 (CTF3). This beam is unique with respect to its long bunch train and high average charge per bunch requirements. The nominal beam for CTF3 consists of 1908 bunches each having a 2.33 nC charge and a bunch frequency of 1.5 GHz. Thus, a total charge of ∼4.4μC has to be extracted and accelerated. The stability of the intensity and the beam parameters along this exceptionally high average current train is crucial for the correct functioning of the CLIC drive beam scheme. Consequently, extensive time-resolved measurements of the transverse and longitudinal beam parameters have been developed, optimized, and performed. The shot-to-shot intensity stability has been studied in detail for the electron and the laser beams, simultaneously. The PHIN photoinjector has been commissioned between 2008 and 2010 during intermittent operations. This paper reports on the obtained results in order to demonstrate the feasibility and the stability of the required beam parameters.

Introduction: In March 2020, the Ontario-based Centre for Effective Practice (CEP) launched an online portal that would become the CEP COVID-19 Resource Centre (CRC), one of Ontario’s most well-known and best-used sources for primary care clinical and practice guidance during the COVID-19 pandemic. Description: Authors will describe how key principles of librarianship drove the development and evolution of the CRC, discuss their approach to literature searching and appraisal in a time of great uncertainty and scant evidence, and outline successes and challenges. Outcomes: With over 170,500 visitors since 2020, the CRC became an invaluable tool for primary care providers in Ontario, across Canada and internationally. 89% of site visitors reported that the CRC enhanced their knowledge of COVID-19 evidence, recommendations and policies. 87% of visitors reported that the Vaccine resource directly informed their practice. Discussion: Authors discuss challenges of the rapid-response format and skills formed by the demands of the pandemic.

In response to the COVID-19 pandemic, the Ontario-based Centre for Effective Practice (CEP) established the COVID-19 Resource Centre (CRC) in March 2020. This platform rapidly became a critical source of clinical and practice guidance for primary care providers, highlighting the importance of effective information synthesis during public health emergencies. The article discusses the development of the CRC, emphasizing the application of librarianship principles in navigating the challenges posed by the pandemic's information overload and the scarcity of evidence. It outlines the strategies for literature searching, appraisal, and evidence synthesis that were employed to ensure the content's accuracy and utility. The CRC's evolution is presented within the context of its goal to efficiently bridge the gap between evidence and clinical practice, underscoring the collaborative efforts and innovative methodologies that contributed to its success. The CRC has served as an invaluable resource, attracting close to 185,000 visitors from Ontario, across Canada, and internationally. According to survey feedback, 89% of users reported enhanced knowledge of COVID-19 evidence and policies, and 87% stated that the vaccine information directly informed their practice. These statistics underscore the CRC's role in supporting informed decision-making among healthcare providers. The CRC marked the CEP's first foray into real-time evidence-based tool development. Facing challenges of expanding information volumes, an unpredictable information landscape, and the need for swift adaptation to new developments, the CRC emerged as a critical resource, enhancing credibility for the CEP, and fostering new partnerships. This journey underscores the importance of librarianship skills-critical appraisal, evidence synthesis, and knowledge translation-in enhancing service delivery.

The Compact Linear Collider (CLIC) is a study for a future linear electron-positron collider based on a two-beam acceleration scheme in which a high-intensity drive beam is decelerated in order to provide the power to accelerate the main beam for collision in the TeV range. The power extracted from the drive beam deteriorates the beam quality and increases the energy spread significantly. Monitoring of the beam properties is therefore challenging but essential. These challenges are being addressed experimentally at the CLIC test facility where up to 55% of the power is extracted from the beam in the test beam line, a small-scale version of the CLIC drive-beam decelerator, leaving the beam with a very wide energy profile. For monitoring of the transverse beam profile and Twiss parameters we use optical transition radiation screens and quadrupole scans. The intra-pulse-train energy spectrum before and after deceleration is measured with segmented beam dumps. In this paper we discuss the performance of these diagnostic devices with a particular emphasis on the large energy spread and its effect on the beam imaging techniques, and with a final outlook to the CLIC drive-beam diagnostics.

The Compact Linear Collider (CLIC) study proposes a multi-TeV, high luminosity, electron-positron linear collider in order to fulfill the current need for a lepton collider. The study has been started in the late 80s at CERN and currently is a joint effort with a collaboration of 40 institutes. An innovative scheme of high peak RF power production for the high accelerating gradient has been proposed for CLIC. The so called \"two-beam scheme\" consists of two beams that are running parallel to each other. One of the beams is to be accelerated for the collision experiments and called \"the main beam\". The second beam of the CLIC scheme is \"the drive beam\" and will be employed for the power production. The quality of the main beam acceleration depends on the stability of the power that is generated by the drive beam. Therefore, the optimization of the drive beam production with the proper time structure and within the required beam dynamics tolerances is one of the most important accelerator physics aspects of the project. Currently in the conceptual level, the baseline design of the drive beam injector consists of a thermionic gun. This electron source has to be combined with a sub-harmonic bunching system in order to provide the required time structure of the drive beam. However, a big disadvantage of this scheme is the parasitic satellite bunches that are produced due to the sub-harmonic bunching system. PHIN photoinjector has been raised as another option in order to replace the existing thermionic gun of CLIC test facility (CTF3) and to form the bases of a source for the CLIC drive beam. The PHIN project is in the framework of the European CARE (Coordinated Accelerator Research in Europe) program.

The BCML system is a beam monitoring device in the CMS experiment at the LHC. As detectors poly-crystalline diamond sensors are used. Here high particle rates occur from the colliding beams scattering particles outside the beam pipe. These particles cause defects, which act as traps for the ionization, thus reducing the CCE. However, the loss in CCE was much more severe than expected. The reason why in real experiments the CCE is so much worse than in laboratory experiments is related to the rate of incident particles. At high particle rates the trapping rate of the ionization is so high compared with the detrapping rate, that space charge builds up. This space charge reduces locally the internal electric field, which in turn increases the trapping rate and hence reduces the CCE even further. In order to connect these macroscopic measurements with the microscopic defects acting as traps for the ionization charge the TCAD simulation program SILVACO was used. Two effective acceptor and donor levels were needed to fit the data. Using this effective defect model the highly non- linear rate dependent diamond polarization as function of the particle rate environment and the resulting signal loss could be simulated.

Measurements of the ratios of charged kaon decay rates for Ke3/K2 π, Kμ3/K2π and Kμ3/Ke3 are presented. These measurements are based on charged kaon decays collected in a dedicated run in 2003 by the NA48/2 experiment at CERN. The results obtained are Ke3/K2π = 0.2470 ± 0.0009 (stat) ± 0.0004 (syst ) and Kμ3/K2π = 0.1637 ± 0.0006 (stat) ± 0.0003 (syst). Using the PDG average for the K2pi normalization mode, both values are found to be larger than the current values given by the Particle Data Book and lead to a larger magnitude of the Vus parameter in the Cabibbo-Kobayashi-Maskawa (CKM) matrix than previously accepted. When combined with the latest Particle Data Book value of |Vud|, |Vus| is in agreement with unitarity of the CKM matrix. A new measured value of the ratio of the semileptonic decay rates, Kμ3/Ke3 = 0.663 ± 0.003(stat) ± 0.001(syst) is compared to semi-empirical predictions based on the latest form factor measurements.

The beam condition monitoring leakage (BCML) system is a beam monitoring device in the compact muon solenoid (CMS) experiment at the large hadron collider (LHC). As detectors 32 poly-crystalline (pCVD) diamond sensors are positioned in rings around the beam pipe. Here, high particle rates occur from the colliding beams scattering particles outside the beam pipe. These particles cause defects, which act as traps for the ionization, thus reducing the charge collection efficiency (CCE). However, the loss in CCE was much more severe than expected from low rate laboratory measurements and simulations, especially in single-crystalline (sCVD) diamonds, which have a low initial concentration of defects. The reason why in real experiments the CCE is much worse than in laboratory experiments is related to the ionization rate. At high particle rates the trapping rate of the ionization is so high compared with the detrapping rate, that space charge builds up. This space charge reduces locally the internal electric field, which in turn increases the trapping rate and recombination and hence reduces the CCE in a strongly non-linear way. A diamond irradiation campaign was started to investigate the rate dependent electrical field deformation with respect to the radiation damage. Besides the electrical field measurements via the Transient Current Technique (TCT), the CCE was measured. The experimental results were used to create an effective deep trap model that takes the radiation damage into account. Using this trap model the rate dependent electrical field deformation and the CCE were simulated with the software SILVACO TCAD. The simulation, tuned to rate dependent measurements from a strong radioactive source, was able to predict the non-linear decrease of the CCE in the harsh environment of the LHC, where the particle rate was a factor 30 higher.