Vacuum birefringence and dichroism signals in the PVLAS experiment Ugo Gastaldi, INFN-LNL Legnaro on behalf of the PVLAS Collaboration ICHEP’06 Moscow Introduction DYCHROISMPRL96,110406(2006) vacuum B induced rotation BIREFRINGENCEQCD-06 and ICHEP-06 vacuum B induced ellipticity Ellipticity measurements PHASE and AMPLITUDE calibrations with gases VACUUM Measurements Outcome VACUUM BIREFRINGENCE has OPPOSITE SIGN of He, Ne,… Birefringence m= meV M= GeV 0++ boson responsible??? Prospects CONFIRM LIGHT BOSON INTERPRETATION by REGENERATION measurements REDUCE NOISE INCREASE DUTY CYCLE PRECISE MEASUREMENTS OF m by changing magnet length

PVLAS Collaboration (Trieste, Pisa, Legnaro, Frascati, Ferrara) : from left to right E.Polacco, E.Milotti, E.Zavattini, R.Cimino, G.Cantatore, S.Marigo, U.Gastaldi, G.Petrucci and A.Zanetti standing G.Zavattini, M.Karuza, G.Ruoso, G.DiDomenico and F.DellaValle seated (S.Carusotto, G.Raiteri and P.Temnikov are not in the picture)

PVLAS EXPERIMENT SITE MAGNET ELLIPSOMETER Fabry-Perot CAVITY MODULATIONS FINESSE ELLIPTICITY CONTROLS OPERATIONS

PVLAS site: two opposite walls of the square pit support the concrete beam (with turntable and cryostat on top) pit floor and pit walls rest on separate foundations

PVLAS top optical bench resting on 4 granite pillars that surround the (rotating) cryostat (with superconducting magnet inside)

Ne run1049_1

N 2 run1110_0

He run1161_0

Ne run1187_0

Run 807_1 Vacuum IR light

run945_5V Vacuum IR light

Run 1101_0 Vacuum Green light

run1137_0 Vacuum Green light

Run 1166_0 Vacuum Green light

run1167_0 Vacuum Green light

November 2005: N 2 +Ne + Vacuum

November 2005: N 2 +He + Vacuum

PVLAS: Vacuum, N 2 and Ne ellipticity phases of runs

PVLAS 1064nm light ISOELLIPTICITY and ISOROTATION curves in (m,M) plane

Physics outcome DICHROISM(IR) amplitude circa (published in PRL2006) ELLIPTICITY(IR) amplitude circa , phase opposite to CME(He, Ne) ELLIPTICITY(Gr) amplitude amplitude circa , phase opposite to CME(He, Ne) If effects observed truly generated mostly by quantum vacuum effects and not by apparatus If microscopic interpretation in terms of existence of ultralight bosons coupled to two photons valid If ultralight bosons have spin zero and only one sort present Phase opposite to CME(noble gases) tells bosons are scalars 0++ m= meV M= GeV

PVLAS oasis in desert of (m,1/M) plane main question: oasis or mirage???

PROSPECTS Confirm LIGHT BOSON interpretation regeneration measurements (in parallel to polarization measur.s) with permanent magnet (beeing purchased to be installed below ellipsometer) Reduce NOISE AMAGNETIC ACCESS STRUCTURE beeing installed PERMANENT MAGNETS planned in place of superconducting m. (no rotating stray field on FP mirrors and other optics elements) Improve SIGNAL Increase DUTY CICLE with permanent magnets (no cryo. constraints) Measure m accurately by changing length L of magnetized volume (in polarization and regeneration measurements)

PVLAS after June 2006 removal of Fe access structure around the vertical granite support of the top optical bench, that surrounds the cryostat

W=20 mwatt out of FP N= in FP, give photons sec-1 passing through PVLAS magnet C= conversion probability in PVLAS magnet 1m long 5.5 Tesla bosons sec-1 boson beams R=16/(4x7.5) reconversion prob. in permanent magnet 0.5m long 2 Tesla expect photons sec-1 regenerated in perm. mag

PVLAS superconducting Morpurgo magnet (assembled with vertical bore) before insertion into warm bore cryostat

Run 1092_0_2 SOM 90 Vacuum B=0

Run 1091_1 Vacuum SOM 90 B=4.35 Tesla Run 1092_0_2 Vacuum SOM 90 B=0 Tesla

B2 dependance of 2omegam signal

Run1091_0 SOM 90 Run1084_0 SOM 0

November 2005, 1ω M peak : N 2 +Ne + Vacuum

November 2005, 1ω M peak : N 2 +He + Vacuum

References Iacopini and Zavattini PL85B(1979)151 Maiani, Petronzio and Zavattini PL B175(1986)359 Raffelt and Stodolsky PR D37 (1988)1237 Cameron et al. (BFST Collab.) PR D47(1993)3707 Rizzo et al. IRPC 16 (1997) 81 and refs. therein Zavattini et al (PVLAS Collab.) PRL 96(2006) Gastaldi arXiv:hep-ex/ (2006) and refs. therein

October 2004: Ne + Vacuum

December 2004: Ne + Vacuum

May 2005: Ne + Vacuum

October 2004, 1ω M peak: Ne + Vacuum

December 2004, 1ω M peak : Ne + Vacuum

May 2005, 1ω M peak : Ne + Vacuum

B dependence: Oct. 2004, Ne 18mbar 2 ω M peak1 ω M peak B2B2 B2B2 B4B4

B dependence: Dec. 2004, Vacuum B2B2 B4B4

PVLAS 532nm and 1024nm light ISOELLIPTICITY curves in (m,M) plane

PVLAS 532 nmlight ISOELLIPTICITY and ISOROTATION curves in (m,M) plane

PVLAS 532nm and 1024nm light ISOROTATION curves in (m,M) plane

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Regeneration scheme with TWO identical OPPOSITE GOING boson beams

Yoke of Morpurgo superconducting magnet

PVLAS Morpurgo magnet : winding of superconducting coils

PVLAS Morpurgo superconducting magnet

PVLAS superconducting Morpurgo magnet before insertion into (liquid He) cryostat

PVLAS superconducting magnet parked in vertical assembly stand

PVLAS cryostat ( with the Morpurgo superconducting magnet inside ) lowered onto the rotating table which rests onto a reinforced concrete beam supported at its extremities by the walls of the square pit of the PVLAS site at INFN-LNL in Legnaro

Top of PVLAS cryostat parked on the floor of the pit in the PVLAS site

PVLAS CRYOSTAT

PVLAS cryostat

PVLAS optical bench below magnet

PVLAS optical bench above magnet

PVLAS installation of amagnetic access structure (Al) to the top optical bench and to the cryostat (July2006)

PVLAS amagnetic access structure