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Muon campus in US and Europe contribution

Periodic Reporting for period 2 - MUSE (Muon campus in US and Europe contribution)

Reporting period: 2018-01-01 to 2019-12-31

The Muon Campus at the Fermi National Laboratory (Fermilab), USA, is a unique world-leading facility providing the most intense pulsed-muon beams and is hosting two world class experiments dedicated to the search for new fundamental interactions beyond those predicted by the Standard Model. Muon (g-2) aims to determine with a ten-fold improvement the anomalous magnetic moment of the muon while Mu2e will improve by four orders of magnitude the sensitivity on the search for the as-yet unobserved Charged Lepton Flavour Violating (CLFV) process of a neutrinoless conversion of a muon to an electron. European research institutions have a leading role in both detector development and construction and in the calibration and analysis of the data. The results from the Fermilab experiments complement those from similar CLFV searches being carried out in Europe and produce very fruitful collaborations in this field. Through an involvement in both the US and the European programs, European institutes are at the forefront of the search for evidence of new physics in the muon sector.

The goal of the MUSE project is to establish new collaborations among European groups participating in the Muon Campus activities, increasing their contribution and visibility at Fermilab and strengthening the already existing partnership with the laboratory. International and intersectoral collaboration is promoted by means of secondments of European personnel from research institutes and small/medium-sized enterprises (SME) and exploiting as much as possible transfer of knowledge among different experiments, institutions and expertise. The ambition of the project is the design, construction, commissioning and calibration of state-of-the-art detectors for the Muon (g-2) and Mu2e experiments and the exploitation of the existing European infrastructure to create a network of radiation hardness tests and characterization of detector components.

During the four years of the project, MUSE has coordinated the activities of about 80 researchers from four European research institute and three SME. State-of-the-art detectors have been designed, built and commissioned, demonstrating that they fulfil the requirements of the experiments. Therefore, the impact of the project matches its initial planning. The activities carried on by the MUSE partners has provided fundamental contributions to the exploitation of the Muon Campus physics goal. The existing EU infrastructures for testing radiation hardness and characterizing the detector components has made the European contribution significantly stronger.
During the four years of the project, state-of-the-art detectors have been successfully designed, built, commissioned and calibrated. The Muon (g-2) straw-tracking system is able to measure the muon beam profile with an accuracy in the vertical plane of better than 10 mrad and efficiently identifies pileup and lost-muon events. The laser monitor systems of the two experiments have been built to monitor the photosensor gain, with the need for Muon (g-2) to reach an accuracy at the sub-per mil level. The Mu2e crystal calorimeter has demonstrated to provide unprecedented timing performance for low energy electrons in the presence of a strong magnetic field, exploiting solid state photosensors, and the Mu2e high-purity germanium detector (HPGe) is able to record X-rays at rates and in radiation levels surpassing previous experiments.

In the framework of the project, it is important to underline the new-born collaboration among MUSE partners for the irradiation tests at European facilities. Several dedicated campaigns took place at ELBE in HZDR and at FNG/CALLIOPE in ENEA during the action. MUSE researchers from all EU research institute, together with US colleagues, tested the radiation hardness of calorimeter components and the functionality of the HPGe detector.

The European research groups participating in the Muon Campus experiments successfully profited from the mutual exchange of skills triggered by MUSE existence, sharing and consolidating different area of expertise in advanced technologies. Notable examples are the already mentioned common work on irradiation damage, the participation of Muon (g-2) laser experts in the design of the Mu2e laser system and the transfer of knowledge on latest generation silicon photosensors for the development of detectors able to monitor online high-intensity laser plasma experiments. Besides the activities among research institutes already discussed, transfer of knowledge takes advantage from the presence of industrial partners, thus enforcing inter-sectoral exchanges.

Trainings of personnel was promoted and supported. MUSE researchers participated to 36 training courses to increase their scientific and soft skills, for a total of 64 participants. Half-day of specific training sessions on advanced topics from research development or industry were organized during annual General Meetings. Moreover, the large number of secondments to Fermilab fostered the opportunity both for young and senior MUSE researchers to come in contact with colleagues from more that 50 research institutes, in a high-quality training environment.

MUSE results have been disseminated to the scientific community through the participations to international conferences and workshops, for a grand total of 107 presentations and posters, and the publication in professional journals (49 peer-reviewed publications and more than 50 contributions to conference proceedings, all in gold/green open access). A lot of effort has been put in outreach activities. Overall, MUSE participated to more than 30 events for the general public and organized twice per year training sessions for university students. MUSE activities have been advertised on the MUSE website and press release for the general public.
Technological challenges adopted to have state-of-the-art detectors, able to operate in the unique environment of the FNAL Muon Campus, find application in different fields. Remarkable examples are the development of electronics components able to survive in high radiation environments, which is an R&D common to space applications, and EMC (Electro-Magnetic Compatibility) compliant equipment that are used in medical instrumentation. Another field of interest for medical imaging is the development of large-area Silicon photosensors able to work in the deep-UV region, opening the possibility of adding timing information to the standard PET imaging.
Radial and vertical beam position measured by the Muon (g-2) straw trackers
The straw trackers in situ inside the vacuum chamber of the Muon (g-2) ring
The optical table in the Muon (g-2) laser hut with lasers and optical components
Rear view of the Mu2e calorimeter Module-0