Towards a direct measurement of vacuum magnetic birefringence: PVLAS achievements |
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Authors: | F Della Valle U Gastaldi R Pengo G Zavattini |
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Institution: | a INFN, Sezione di Trieste and Dipartimento di Fisica, Università di Trieste, Via Valerio 2, 34127 Trieste, Italy b INFN, Sezione di Ferrara and Dipartmento di Fisica, Università di Ferrara, Via Saragat 1, Blocco C, 44100 Ferrara, Italy c INFN, Laboratori Nazionali di Legnaro, viale dellUniversità 2, 35020 Legnaro, Italy |
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Abstract: | Nonlinear effects in vacuum have been predicted but never observed yet directly. The PVLAS collaboration has long been working on an apparatus aimed at detecting such effects by measuring vacuum magnetic birefringence. Unfortunately the sensitivity has been affected by unaccounted noise and systematics since the beginning. A new small prototype ellipsometer has been designed and characterized at the Department of Physics of the University of Ferrara, Italy entirely mounted on a single seismically isolated optical bench. With a finesse F = 414,000 and a cavity length L = 0.5 m we have reached the sensitivity of given the laser power at the output of the ellipsometer of P = 24 mW. This record result, very close to the predicted limit, demonstrates the feasibility of reaching such sensitivities, and opens the way to designing a dedicated apparatus for a first detection of vacuum magnetic birefringence. |
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