PHELEX:
Present Status
Anatoly Kopylov
Institute for Nuclear Research of RAS, Moscow
Collaborators: Igor Orekhov, Valery Petukhov et al.

The aim of experiment:
to search for Dark Matter
Zwicky (1937) – analyses of red shifts of the Coma Cluster of galaxies:
surprisingly high mass-to-light ratio
Enigma 1: to-day, according to a combination of all data: the dark matteraccounts for about 84 % of the matter content of the Universe (Planck 2018results)
Enigma 2: why dark matter is distributed in galaxy by a spherical halo
while baryonic matter – in the plane of galaxy ?
 CDM is not particles but waves, mγ’ < 100 eV

Lam Hui arXiv:2101.11735v1

Why Dark Matter?

P. Salucci arXiv:1811.08843

3
A.Kopylov 20th Lomonosov Conference, Moscow 2021

The dark Photon

M. Fabbrichesi, E. Gabrielli, G. Lanfranchi
The Physics of the Dark Photon, Springer Briefs in Physics (Springer, 2021)

4

PHELEX – PHoton-ELectron EXperimentmulticathode counter technique as an extension ofa method of a dish antenna to higher masses (energies)

P  2 2  2  CDM Adish 2  cos 2  θ – angle between a field of a hidden photon and the surface
χ- dimensionless parameter quantifying a kinetic mixing

ρCDM ≈ 0.3 GeV/cm3ρ

⊙= (0.43 ± 0.06) GeV/cm3 (Salucci et al 2010)

Galactic dark matter halo.
(D.Horns, J.Jackel, A.Lindner, A.Lobanov, J.Redondo, A.Ringwald , But locally, near the Sun?
“Searching for wispy cold dark matter with a dish antenna” JournalPrimordial Solar dark matter halo?
of Cosmology and Astroparticle Physics, vol.4. article 16, 2013) arXiv:2007.11016(N.B.Anderson, A.Partenheimer,and T.D.Wiser)
In our case: due to low reflectivity of the surface
the photon gets absorbed and emits an electron

P  RMCC m ' / Sensitivity:

5A.Kopylov 20th Lomonosov Conference, Moscow 2021

Multicathode counter technique
as an extension of a method of dish-antenna12111

 R  m '  2  0.3GeV / cm 3  2  1m 2  2  2 / 3   2.9 10 12  MCC        CDM  1Hz   1eV    Acath    

A.Kopylov 20th Lomonosov Conference, Moscow 2021

6

Multicathode counter: assembling and testing7

Single-electron pulses

Polya distribution

Pulse from muon crossing the counter

Pulse from single electron

From muons at sea level: ≈ 15 pulses per second  ≈ 15% dead time (10 ms per each pulse)

8
A.Kopylov 20th Lomonosov Conference, Moscow 2021

Principle of a multicathode counter:
Retarding potential of the second cathode in configuration 2

The effect: rMCC = R1 – R2
HV2

HV1

ΔU = HV2 – HV1
A.Kopylov 20th Lomonosov Conference, Moscow 2021

R1 – red, R2 - blue

9

Results of measurementswith Ar +CH4(10%) and Ne + CH4(10%) gas mixtures
The target – free electrons of a degenerate electron gas of a metal
Result is included in compilation of the data
Review of Particle Physics in Prog. Theor. Exp. Phys. 2020, 083C01 (2020).
HV2

HV1

R1 – red, R2 - blue•
rMCC = (- 0.33 ± 0.7)˖10-6 Hz/cm2
A.Kopylov 20th Lomonosov Conference, Moscow 2021

Target – valence electrons10Directionality of the counting22P  2   CDM Adish 2  cos2 θ – angle between a fieldof a hidden photon andthe surface
χ- dimensionlessparameter quantifying akinetic mixing

Field along the axes of the counter cos 2   0

Field normal to the axes of the counter cos 2  •

12

By rotation of the counter –variation of the count rate
A.Kopylov 20th Lomonosov Conference, Moscow 2021

(D.Horns, J.Jackel, A.Lindner,
A.Lobanov, J.Redondo,
A.Ringwald , “Searching forwispy cold dark matter with adish antenna” Journal ofCosmology and AstroparticlePhysics, vol.4. article 16,2013)

If the surface is mirror-like!
The counter with a matt surface –for the control measurements

11

Diurnal variations, Baksan, Russia 43º<α2> averaged for 1 hour

Vertical orientation

East-West orientation

North-South orientation

12
A.Kopylov 20th Lomonosov Conference, Moscow 2021

Diurnal variations, INO, India 10º

Vertical orientation

East-West orientation

North-South orientation

13
A.Kopylov 20th Lomonosov Conference, Moscow 2021

Diurnal variations, Pyhäsalmi, Finnland 64º

Vertical orientation

East-West orientation

North-South orientation

14
A.Kopylov 20th Lomonosov Conference, Moscow 2021

Red – configuration 1Blue – configuration 2871 points;
In previousmeasurements – 200points

New measurements Al – (Ne + CH4(10%) 1 Bar)
A.Kopylov 20th Lomonosov Conference, Moscow 2021

15

C1-C2 = - 0.00018 ± 0.00101 (2σ)
RMCC = (C1 –C2 + 2σ)/ε = 0.00184/0.608
ε – efficiency of counting
Previous measurements:
C1-C2 = - 0.00098 ± 0.00211 (2σ)
RMCC = (C1 –C2 + 2σ)/ε = 0.00323/0.616

New upper limit
12111 R  m '  2  0.3GeV / cm 3  2  1m 2  2  2 / 3   2.9 10 12  MCC        CDM  1Hz   1eV    Acath    

A.Kopylov 20th Lomonosov Conference, Moscow 2021

16

Diurnal variations of the count rates inconfig.1, config.2 and (config.1 + config.2)
A.Kopylov 20th Lomonosov Conference, Moscow 2021

17

Diurnal variations in solar (red) and stellar (blue) frames
one solar day = 24 hours, one sidereal day = 23 hours 56 minutes
A.Kopylov 20th Lomonosov Conference, Moscow 202118

Substantial difference of the diurnal run for three detectors
at each latitude that will enable for sufficiently large samples of data to
determine the absolute phase of the diurnal run and thus to find the absolute
direction of the vector of the E-field.

Installation with 4 multicathode counters
1,2,3 – counters withthe mirror cathodes,
4 – counter with amatt cathode5 – lead bricks
6 – thermal insulation
7 – metallic housing
8 – impregnated wood
9 – cooling by air19

Summary
The method is working and first results areencouraging
The observation (if any) of diurnal variations promises
a discovery and will enable to determine a direction ofa vector of E-field in Solar or Stellar frame
The study can be performed by independent groups indifferent mines at different geographical latitudes
what will increase the reliability of the resultsOur publications:
1. A.K., I.Orekhov, V.Petukhov, On the possibility of observing diurnalvariations in the count rate of dark photons using a multicathode counters,
Physics of Particles and Nuclei, 2021, Vol.52, No.1, pp. 31 - 38
2. A.K., I.Orekhov, V.Petukhov, First results and future prospects withPHELEX, Journal of Physics, Conference Series, 1690 (2020) 012002,
doi:10.1088/1742-6596/1690/1/012002
3. A.K., I.Orekhov, V.Petukhov, Results from a hidden photon dark mattersearch using a multi-cathode counter, JCAP, 07, 008 (2019)
4. A.K., I.Orekhov, V.Petukhov, Method of search for hidden photons of Cold
Dark Matter using a multi-cathode counter, Physics of Atomic Nuclei, Vol.82,
No. 9, pp 1-8, (2019)
5. A.K., I.Orekhov, V.Petukhov, Search for Hidden Photon Dark Matter using aMulti-Cathode Counter. Proceedings of the 4th International Conference on
Particle Physics and Astrophysics (ICPPA-2018), Journal of Physics:
Conference Series, 1390 (2019) 012066
6. A.K., I.Orekhov, V.Petukhov, A multi-cathode counter in a single-electron
counting mode, NIM A, 910, 164 (2018)
7. A.K., I.Orekhov, V.Petukhov, Tech. Phys. Lett 42, 102 (2016)
8. A.K., I.Orekhov, V.Petukhov, Adv. High Energy Phys., 2058372 (2016)

A.Kopylov 20th Lomonosov Conference, Moscow 2021

21

Thank you22A.Kopylov 20th Lomonosov Conference, Moscow 2021