arXiv subjects

A. P. Serebrov

Publications and source records attributed to A. P. Serebrov.

49 records · Page 3Linked to original sources

arXiv2009

Comment for article "Limits on a nucleon-nucleon monopole-dipole (axionlike) P,T-noninvariant interaction from spin relaxation of polarized 3He" Yu. N. Pokotilovski arXiv:0902.1682v2 [nucl-ex] 12 Feb 2009

In article "Limits on a nucleon-nucleon monopole-dipole (axionlike) P,T-noninvariant interaction from spin relaxation of polarized 3He" Yu. N. Pokotilovski arXiv:0902.1682v2 [nucl-ex] 12 Feb 2009 it was presented new constraints for the product of the scalar, pseudo-scalar dimensionless constants: gs*gp < 1*10^-17 for the parameter lam about 10^-4 cm, determining the range of forces. In this comment it is shown that the real constraint for the same parameter lam from the same experimental data is about 2*10^-11. It is worse in about one hundred times that the constraint from UCN depolarization and can not be considered as a new limit on a nucleon-nucleon monopole-dipole (axionlike) P,T-noninvariant interaction.

nucl-ex↗

arXiv2009

Search for macroscopic CP violating forces using a neutron EDM spectrometer

The search for CP violating forces between nucleons in the so-called axion window of force ranges lam between 2x10^-5 m and 0.02 m is interesting because only little experimental information is available there. Axion-like particles would induce a pseudo-magnetic field for neutrons close to bulk matter. A laboratory search investigates neutron spin precession close to a heavy mirror using ultracold neutrons in a magnetic resonance spectrometer. From the absence of a shift of the magnetic resonance we established new constraints on the coupling strength of axion-like particles in terms of the product gs x gp of scalar and pseudo-scalar dimensionless constants, as a function of the force range lam, gs x gp x lam^2 <= 2x10-21 [cm^2] (C.L.95%) for 10^-4 cm < lam < 1 cm. For 0.1 cm < lam < 1 cm previous limits are improved by 4 to 5 orders of magnitude.

nucl-ex↗

arXiv2009

On Continuum-State and Bound-State Beta Decay Rates of the Neutron

We analyse the continuum-state and bound-state beta^-decay rates of the neutron. For the calculation of theoretical values of the decay rates we use the new value for the axial coupling constant g_A = 1.2750(9), obtained recently by H. Abele (Progr. Part. Nucl. Phys., 60, 1 (2008)) from the fit of the experimental data on the neutron spin-electron correlation coefficient of the electron energy spectrum of the continuum-state beta^- decay of the neutron. We take into account the contribution of radiative corrections and the scalar and tensor weak couplings. We define correlation coefficients of the electron energy spectrum in terms of axial, scalar and tensor coupling constants. Using recent precise experimental data for the lifetime of the neutron and correlation coefficients we estimate the scalar and tensor weak coupling constants. The bound-state beta^- decay rates of the neutron we calculate as functions of axial, scalar and tensor weak coupling constants. We show that dominantly the neutron decays into hydrogen in the hyperfine states with total angular momentum F = 0. The calculated angular distributions of the probabilities of the bound-state beta^- decays of the polarised neutron can be used for the experimental measurements of the bound-state beta^- decays into the hyperfine states with a total angular momentum F = 1.

hep-ph↗

arXiv2009

Comment for article "Limits on a nucleon-nucleon monopole-dipole (axionlike) P-,T-noninvariant interaction from spin relaxation of polarized ultracold neutrons" Yu.N. Pokotilovski, arXiv:0902.3425v2

In work [1] (Yu. N. Pokotilovski, arXiv:0902.3425v2) restrictions on constants of pseudo-magnetic interaction gSgP are presented. These restrictions are considerably differed from restrictions on gSgP, before published in work [2] (A.P. Serebrov, arXiv:0902.1056v1). Restrictions in work [1] are received from the same experimental data which are used in work [2], however difference in restrictions is considerable. This difference is changed in a range from 1 to 10^7 times depending on value lambda. In the given work it is shown that restrictions of work [1] are wrong and the possible reasons of the admitted errors are considered.

nucl-ex↗

arXiv2009

Preparation of facilities for fundamental research with ultracold neutrons at PNPI

The WWR-M reactor of PNPI offers a unique opportunity to prepare a source for ultracold neutrons (UCN) in an environment of high neutron flux (about 3*10^12 n/cm^2/s) at still acceptable radiation heat release (about 4*10^-3 W/g). It can be realized within the reactor thermal column situated close to the reactor core. With its large diameter of 1 m, this channel allows to install a 15 cm thick bismuth shielding, a graphite premoderator (300 dm^3 at 20 K), and a superfluid helium converter (35 dm^3). At a temperature of 1.2 K it is possible to remove the heat release power of about 20 W. Using the 4pi flux of cold neutrons within the reactor column can bring more than a factor 100 of cold neutron flux incident on the superfluid helium with respect to the present cold neutron beam conditions at the ILL reactor. The storage lifetime for UCN in superfluid He at 1.2 K is about 30 s, which is sufficient when feeding experiments requiring a similar filling time. The calculated density of UCN with energy between 50 neV and 250 neV in an experimental volume of 40 liters is about 10^4 n/cm^3. Technical solutions for realization of the project are discussed.

nucl-ex↗

arXiv2009

Monte Carlo simulation of the experiment MAMBO I and possible correction of neutron lifetime result

We are discussing the present situation with neutron lifetime measurements. There is a serious discrepancy between the previous experiments and the recent precise experiment [1]. The possible reason of the discrepancy can be connected with a quasi-elastic scattering of UCN on the surface of liquid fomblin which was used for most of the previous experiments. The Monte Carlo simulation of one of the previous experiments [2] shows that the result of this experiment [2] has to be corrected and instead of the previous result 887.6 +/- 3 s the new result 880.4 +/- 3 s has to be claimed. [1] A.P. Serebrov et al., Phys. Lett. B 605 (2005) 72. [2] W. Mampe et al., Phys. Rev. Lett. 63 (1989) 593.

nucl-ex↗

arXiv2009

Search for neutron - mirror neutron oscillations in a laboratory experiment with ultracold neutrons

Mirror matter is considered as a candidate for dark matter. In connection with this an experimental search for neutron - mirror neutron (nn') transitions has been carried out using storage of ultracold neutrons in a trap with different magnetic fields. As a result, a new limit for the neutron - mirror neutron oscillation time has been obtained, tau_osc >= 448 s (90% C.L.), assuming that there is no mirror magnetic field larger than 100 nT. Besides a first attempt to obtain some restriction for mirror magnetic field has been done.

nucl-ex↗

arXiv2009

New constraints for CP-violating forces between nucleons in the range 10-4 cm - 1 cm

The range of nucleon interaction 10-4 cm - 1 cm is interesting because it corresponds to the mass range of a intermediate particle inside so named "axion window" that is not closed yet by experiment. Depolarization of ultracold neutrons (UCN) during their storage in material traps can be caused by CP-violating pseudo-magnetic precession of the neutron spin in the vicinity of the unpolarized substance surface. Using the experimental limits for UCN depolarization new constraints were set for the product of the scalar, pseudo-scalar dimensionless constants gS*gP and the parameter lam_PS, determining the Yukawa-type of the nucleon interaction potential via new pseudo-scalar boson (axion-like particle) with a mass of m_PS: gS*gP*lam_PS^2 <= 2.96*10-21 [cm^2] for 10-3 cm < lam_PS < 1 cm; gS*gP*lam_PS^2 <= 3.9*10-22 [cm^2] for 10-4 cm < lam_PS < 10-3 cm. Improvement of the limit for gS*gP in the area of lam_PS from 0.1 cm to 1 cm accounts for 4-5 orders of magnitude in comparision with previous limit. The prospects of increasing in accuracy search for CP-violating pseudo-magnetic precession are considered. The estimations of the possible effects of pseudo-magnetic precession in the frame of the theoretical models with CP-violation are discussed.

nucl-ex↗

arXiv2009

Neutron lifetime measurements using gravitationally trapped ultracold neutrons

Our experiment using gravitationally trapped ultracold neutrons (UCN) to measure the neutron lifetime is reviewed. Ultracold neutrons were trapped in a material bottle covered with perfluoropolyether. The neutron lifetime was deduced from comparison of UCN losses in the traps with different surface-to-volume ratios. The precise value of the neutron lifetime is of fundamental importance to particle physics and cosmology. In this experiment, the UCN storage time is brought closer to the neutron lifetime than in any experiments before:the probability of UCN losses from the trap was only 1% of that for neutron beta decay. The neutron lifetime obtained,878.5+/-0.7stat+/-0.3sys s, is the most accurate experimental measurement to date.

nucl-ex↗

arXiv2007

Experimental search for neutron - mirror neutron oscillations using storage of ultracold neutrons

The idea of a hidden sector of mirror partners of elementary particles has attracted considerable interest as a possible candidate for dark matter. Recently it was pointed out by Berezhiani and Bento that the present experimental data cannot exclude the possibility of a rapid oscillation of the neutron n to a mirror neutron n' with oscillation time much smaller than the neutron lifetime. A dedicated search for vacuum transitions n->n' has to be performed at weak magnetic field, where both states are degenerate. We report the result of our experiment, which compares rates of ultracold neutrons after storage at a weak magnetic field well below 20 nT and at a magnetic field strong enough to suppress the seeked transitions. We obtain a new limit for the oscillation time of n-n' transitions, tau_osc (90% C.L.) > 414 s. The corresponding limit for the mixing energy of the normal and mirror neutron states is delta_m (90% C.L.) < 1.5x10-18 eV.

nucl-ex↗

arXiv2007

Comment to the article "Possible Systematic Effects in Fomblin Coated Storage Cell Neutron Lifetime Measurements", Steve K. Lamoreaux [1]

The author of article discusses the possible systematic effects in our experiment using reference and picture from allegedly our publication. First of all this publication does not exist. The assumption of author about the probability of lower energy upscattering is in a rough contradiction (300 times) with our experimental limit which is extremely lower, about 6x10-9 per neutron collision. The second assumption of author concerning quasi-stable orbits of UCN with higher energy due to specular neutron reflection from trap wall is also in a rough contradiction with our experimental data clear demonstrated in our previous articles as well in the last very detailed article recently presented in the arXiv. We are very surprised that author discusses well known questions studied in our experiment in details.

nucl-ex↗

arXiv2007

Neutron beta-decay, Standard Model and cosmology

The precise value of the neutron lifetime is of fundamental importance to particle physics and cosmology. The neutron lifetime recently obtained, 878.5 +/- 0.7stat +/- 0.3sys s, is the most accurate one to date. The new result for the neutron lifetime differs from the world average value by 6.5 standard deviations. The impact of the new result on testing of Standard Model and on data analysis for the primordial nucleosynthesis model is scrutinized.

nucl-ex↗

arXiv2005

Method of study of nanostructures by ultracold neutrons

We propose a new method to form very cold neutron (VCN) beams collimated and monochromatic without usual losses of flux by three or more orders in magnitude due to narrow line cutting from energy and angular spectra. To this purpose ultracold neutrons should be accelerated in gravity field to shift their phase volume in momentum space without volume expansion. The possibilities and advantages of VCN in studies of nanostructures, the results of modelling of scattering on various nanoobjects by the real resolution of VCN-diffractometer are discussed.

cond-mat.other↗