Tests of the Weak Equivalence Principle with UCNs A.F. Frank frank@nf.jinr.ru International Workshop " Probing Fundamental Symmetries and Interactions with UCN ". Mainz, April 11th-15th, 2016 1
Outline • Neutrons and gravity (short review) • Moving grating and the experiment of 2006 • Moving grating, flux modulation and the experiment of 2010-2012. • Moving grating and Fountain experiment • Road map to the new gravity experiment 2 A. Frank. UCN workshop, Mainz, 2016
1. g =935 70cm/sec 2 2. J.W.Dabbs,J.A.Harvey, D.Pava and H.Horstmann, 1965 g(002)=973.1 7.4cm/sec 2 g loc = 979.74cm/sec 2 g(100)=975.1 3.1cm/sec 2 3 A. Frank. UCN workshop, Mainz, 13 April, 2016
L.Koester , 1976 2 2 mgh U b 0 eff m 2 2 2 m g loc m g h b 1- = 3 10 -4 V.F.Sears,1982 g n 0 m m m g i i g n 1- = 1.00011 0.00017 J. Schmiedmayer, NIM A 284, (1989) 59 4 A. Frank. UCN workshop, Mainz, 13 April, 2016
Koester’s experiment and the problem of n -e scattering When the value of b coh extracts from the total cross section data it is necessary to take into account the n-e scattering. For the case of Pb and Bi correspondent corrections are of the order 1%. Consequently, if one aim to reach 10 -4 in precision of b coh the amplitude of n-e scattering must be known with precision of 1%. It is not evident that b ne is known with such precision even now Schmiedmayer used statistically inconsistent data for n-e scattering 5 A. Frank. UCN workshop, Mainz, 13 April, 2016
Koester’s experiment and effective potential 2 2 mgH U b eff m What is a precision of the above equation for the effective potential U? V.F.Sears (1982); M. Warner, J.E Gubernatis. (1985) Lax, 1951 Theory: (estimation for lead at V n 400 m/sec) – corrections of the order of 5 10 -5 There are no any experiments for the test of theory with precision better than some percent 6 A. Frank. UCN workshop, Mainz, 13 April, 2016
Neutron Interferometric Experiments (COW – type experiment) R.Colella, A,W.Overhauser and S.A. Werner (COW), 1975 The experimentally obtained values for the gravitationally induced phase factor were lower than the theoretically expected value by 1.5% for the skew-symmetric interferometer data and 0.8% for the symmetric interferometer data in measurements with relative uncertainties of 0.12% and 0.11%, respectively. K.S.Litrell, B.E.Allman and S.A.Werner, 1997 7 A. Frank. UCN workshop, Mainz, 13 April, 2016
1- = (1 ± 9) 10 -3 8 A. Frank. UCN workshop, Mainz, 13 April, 2016
Test of the weak equivalence principle for neutrons (2006) E E 0 E H H The idea was to compare the change of energy mgH with energy ħΩ transferred to neutron by a moving grating Frank A.I., Masalovich S.V., Nosov V.G. (ISINN-12). E3-2004-169, 215, Dubna, (2004) ΔΩ m g = i n ΔH 9 A. Frank.UCN workshop, Mainz, 13 April, 2016
Moving diffraction grating as a nonstationary device e − ik z z V y z 0 1 -1 ΔE = Ω 2 -2 E E = ω 0 (z,y,t) a exp[i( k z q y t ] ) j j j j j 1 V – grating velocity 2 V 2 j k k 1 j L – period of grating j 0 j 0 L 0 10 A. Frank.UCN workshop, Mainz, 13 April, 2016
Moving (rotating) diffraction grating as a nonstationary device Phase π -grating UCN Monochromator n d L k ( n 1 ) d ΔE = Ω ΔE = Ω 1 where N is number of groves -1 N = 75398 E 11 A. Frank.UCN workshop, Mainz, 13 April, 2016
Fabry-Perot interferometers (Neutron Interference filters) as a spectrometric device Energy of the state 1,0 0,8 Transmission 0,6 0,4 0,2 0,0 0 50 100150 200250 300 350400 450500 Substrate 1 2 1 Energy (neV) 2 2 2 U b 1 , 2 1 , m 12 A. Frank.UCN workshop, Mainz, 13 April, 2016
Experimental results 4,0 f=45Hz f=55Hz f = 64 Hz 3,5 f =75Hz f =95Hz 2 N f =105Hz B th = 0.304203 B 3,0 Count rate (c/sec) th mg loc 2,5 2,0 B exp = 0.3037 ± 0.00065 1,5 1,0 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 Distance betwee the filter (cm) m g 3 n loc 1 (1.8 2.1) 10 35 m g i n 30 A.I. Frank, P. Geltenbort, M. Jentschel,et al. Fitted H max 25 JETP Letters, 86, 225 (2007) 20 h 0 = c +B*f g 15 3 loc 1 (1.8 2.1) 10 g 10 n 40 50 60 70 80 90 100 110 Rotation frequency (rot/sec) 13 A. Frank. UCN workshop, Mainz, 13 April, 2016
Experiment of 2010-2012. Flux modulation Flux modulation Comparing the energy mgH with energy ħΩ as before TOF base Combination of Neutron E 1 Interference Filters with peculiar TOF spectrometry E 2 E 1 >E 2 >E 3 E 3 Count-rate oscillations on a detector φ = 2πft 14 A. Frank.UCN workshop, Mainz, 13 April, 2016
Experiment of 2010-2012. Part I Calibration Modulation frequency 75Hz 80 Total p hase of the count rate modulation 78 76 Monochromator 74 φ = f ( E a − m g g n H ) 72 70 Detector 15 20 25 30 35 40 45 Positon of carriage (mm) Calibration Variation of the monochromator vertical position leads to changing of the UCN energy, time of flight and total phase of the count rate oscillation 15 A. Frank. UCN workshop, Mainz, 13 April, 2016
Experiment of 2010-2012. Part II (idea) 80 Total p hase of the count rate modulation Monochromator Monochromator 78 φ= f E Ω mon φ= f E 76 mon grating grating φ= f E Ω mon 74 72 70 Detector Detector 15 20 25 30 35 40 45 Position of the carriage (mm) The count rate oscillation phase of the UCN which energy shifted by rotating grating must be compared with the calibration curve Unfortunately -1 order of diffraction is accompanied by the +1 and diffraction. orders of higher orders 16 A. Frank.UCN workshop, Mainz, 13 April, 2016
Using special 9-layers filter with wide transmission band we selected the line of the -1 diffraction order 0 0 Monochromator 1 1 -1 -1 ΔE = ΔE = Ω Ω 2 2 -2 -2 1,0 E E E = ω E = ω 0,8 0 0 grating Transmittivity 0,6 12 neV Wide- 2000 analyzer 1800 0,4 1600 1400 1200 0,2 Counts 1000 800 600 0,0 400 200 Detector 90 100 110 120 130 0 100 110 120 130 140 E, (nev) E , neV 17 A. Frank.UCN workshop, Mainz, 13 April, 2016
Experiment 2010-2012. Part II (idea) Monochromator 80 Total p hase of the count rate modulation 78 φ= f E Ω mon 1 grating 76 Wide φ= f E Ω 74 analyzer mon 2 Δ H 72 ΔΩ m g = i n ΔH 70 Detector 15 20 25 30 35 40 45 Position of the carriage (mm) The count rate oscillation phase of the UCN which energy shifted by the grating rotating with different frequency must be compared with the calibration curv 18 A. Frank.UCN workshop, Mainz, 13 April, 2016
Experiment of 2010-2012. 19 A. Frank.UCN workshop, Mainz, 13 April, 2016
Experiment of 2010-2012 . Found problem 80 Total p hase of the count rate modulation 78 φ= f E Ω 76 mon 74 φ= f E Ω mon 72 70 15 20 25 30 35 40 45 Position of the carriage (mm) The role of the even diffraction orders was underestimated 20 A. Frank. UCN workshop, Mainz, 13 April, 2016
Experiment of 2010-2012 . Found problem 80 Total p hase of the count rate modulation 78 φ= f E Ω 76 mon 74 φ= f E Ω mon 72 a x' b 70 x' 15 20 25 30 35 40 45 Position of the carriage (mm) The role of the even diffraction orders was underestimated 21 A. Frank. UCN workshop, Mainz, 13 April, 2016
The present status of experiment (2014) 1. The full scale test measurements with new spectrometer was performed. 2. The rate of the collection of statistical accuracy, was obtained as 5 × 10 -3 per day. That is enough to collect statistical accuracy of the order of 5 × 10 -4 during two cycle of statistic collection at PF2 source. 3. It was realized that it is rather difficult to exclude the systematic effect due to admixture of the neighbor (even) diffraction orders to the spectrum of minus first order. 4. The parasitic high energy line which may disturbs the phase of the count rate oscillation was found 12 114 nev 1,0 10 0,8 8 Transmission INt (arb. units) 0,6 6 0,4 4 255 neV 0,2 2 0 0,0 0 50 100 150 200 250 300 350 400 450 100 150 200 250 300 350 Energy (neV) Energy (neV) 22 A. Frank.UCN workshop, Mainz, 13 April, 2016
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