arXiv subjects

Y. Valdau

Publications and source records attributed to Y. Valdau.

11 recordsLinked to original sources

arXiv2026

First Experimental Limit on the Permanent Electric Dipole Moment of the Deuteron

Permanent electric dipole moments (EDMs) provide a sensitive probe of physics beyond the Standard Model and are directly linked to additional sources of CP violation that could explain the matter-antimatter asymmetry of the universe. EDM measurements of charged particles in storage rings rely on detecting a small tilt of the invariant spin axis with respect to the ring plane. In this work, we present the experimental determination of the invariant spin axis of an ensemble of deuterons in the COoler SYnchrotron (COSY), a conventional magnetic storage ring, using a combination of a radio-frequency Wien filter, a superconducting Siberian snake and an electron-cooler solenoid. The measurements reveal tilts of a few milliradians, which are dominated by systematic effects. From the observed tilts, we derive the first experimental limit on the deuteron EDM, $|d^d|< 2.5\cdot10^{-17}\,e\cdot\mathrm{cm} \; (95\%\,\text{ C.L.})$. This result demonstrates the feasibility of using storage rings to search for EDMs of charged stable hadrons and provides a foundation for future dedicated facilities.

nucl-ex↗

arXiv2025

Maintaining a Resonance Condition of an RF Spin Rotator Through a Feedback Loop in a Storage Ring

This paper presents the successful application of a phase-lock feedback system to maintain the resonance condition of a radio frequency (rf) spin rotator (specifically, an rf Wien filter) with respect to a 120 kHz spin precession in the Cooler Synchrotron (COSY) storage ring. Real-time monitoring of the spin precession and the rf Wien filter signal allows the relative phase between the two to be stabilized at an arbitrary setpoint. The feedback system compensates for deviations in the relative phase by adjusting the frequency and/or phase as needed. With this method, a variation in phase relative to the demand phase with a standard deviation of $σ_{Δφ}\approx 0.2\mathrm{rad}$ could be achieved. The system was implemented in two runs aiming at a first direct measurement of the deuteron electric dipole moment in 2018 and 2021. In addition, the difference between a single-bunch beam affected by the spin rotator and a two-bunch system in which only one bunch is exposed to the spin rotator fields is discussed. Both methods have been used during these beam times. The ability to keep the spin precession and the rf fields synchronized is also crucial for future investigations of electric dipole moments of charged particles using storage rings.

physics.acc-ph↗

arXiv2023

Spin decoherence and off-resonance behavior of radiofrequency-driven spin rotations in storage rings

Radiofrequency-driven resonant spin rotators are routinely used as standard instruments in polarization experiments in particle and nuclear physics. Maintaining the continuous exact parametric spin-resonance condition of the equality of the spin rotator and the spin precession frequency during operation constitutes one of the challenges. We present a detailed analytic description of the impact of detuning the exact spin resonance on the vertical and the in-plane precessing components of the polarization. An important part of the formalism presented here is the consideration of experimentally relevant spin-decoherence effects. We discuss applications of the developed formalism to the interpretation of the experimental data on the novel pilot bunch approach to control the spin-resonance condition during the operation of the radiofrequency-driven Wien filter that is used as a spin rotator in the first direct deuteron electric dipole moment measurement at COSY. We emphasize the potential importance of the hitherto unexplored phase of the envelope of the horizontal polarization as an indicator of the stability of the radiofrequency-driven spin rotations in storage rings. The work presented here serves as a satellite publication to the work published concurrently on the proof of principle experiment about the so-called pilot bunch approach that was developed to provide co-magnetometry for the deuteron electric dipole moment experiment at COSY.

physics.acc-ph↗

arXiv2023

Pilot bunch and co-magnetometry of polarized particles stored in a ring

In polarization experiments at storage rings, one of the challenges is to maintain the spin-resonance condition of a radio-frequency spin rotator with the spin-precessions of the orbiting particles. Time-dependent variations of the magnetic fields of ring elements lead to unwanted variations of the spin precession frequency. We report here on a solution to this problem by shielding (or masking) one of the bunches stored in the ring from the high-frequency fields of the spin rotator, so that the masked pilot bunch acts as a co-magnetometer for the other signal bunch, tracking fluctuations in the ring on a time scale of about one second. While the new method was developed primarily for searches of electric dipole moments of charged particles, it may have far-reaching implications for future spin physics facilities, such as the EIC and NICA.

physics.ins-det↗

arXiv2021

First detection of collective oscillations of a stored deuteron beam with an amplitude close to the quantum limit

We investigated coherent betatron oscillations of a deuteron beam in the storage ring COSY, excited by a detuned radio-frequency Wien filter. The beam oscillations were detected by conventional beam position monitors. With the currently available apparatus, we show that oscillation amplitudes down to \SI{1}{\micro \meter} can be detected. The interpretation of the response of the stored beam to the detuned radio-frequency Wien filter is based on simulations of the beam evolution in the lattice of the ring and realistic time-dependent 3D field maps of the Wien filter. Future measurements of the electric dipole moment of protons will, however, require control of the relative position of counter-propagating beams in the sub-picometer range. Since here the stored beam can be considered as a rarefied gas of uncorrelated particles, we moreover demonstrate that the amplitudes of the zero-point (ground state) betatron oscillations of individual particles are only a factor of about 10 larger than the Heisenberg uncertainty limit. As a consequence of this, we conclude that quantum mechanics does not preclude the control of the beam centroids to sub-picometer accuracy. The smallest Lorentz force exerted on a single particle that we have been able to determine is \SI{10}{aN}.

nucl-ex↗

arXiv2021

Storage Ring to Search for Electric Dipole Moments of Charged Particles -- Feasibility Study

The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly $^3$He) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10$^{-29}$ e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation from the longitudinal to the vertical direction. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. A stepwise plan is foreseen, starting with ongoing COSY activities that demonstrate technical feasibility. Achievements to date include reduced polarization measurement errors, long horizontal plane polarization lifetimes, and control of the polarization direction through feedback from scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally a high-precision electric-field storage ring.

hep-ex↗

arXiv2014

Absence of spin dependence in the final state interaction of the d(pol) p --> 3He eta reaction

The deuteron tensor analysing power t_{20} of the d(pol) p --> 3He eta reaction has been measured at the COSY-ANKE facility in small steps in excess energy Q up to Q = 11 MeV. Despite the square of the production amplitude varying by over a factor of five through this range, t_{20} shows little or no energy dependence. This is evidence that the final state interaction causing the energy variation is not influenced by the spin configuration in the entrance channel. The weak angular dependence observed for t_{20} provides useful insight into the amplitude structure near threshold.

nucl-ex↗

arXiv2014

Isospin effects in the exclusive dp -> 3Heπ+π- reaction

The differential cross section for the exclusive dp -> 3Heπ+π- reaction has been measured with high resolution and large statistics over a large fraction of the backward 3He hemisphere at the excess energy 265 MeV using the COSY-ANKE magnetic spectrometer. Though the well-known ABC enhancement is observed in the π+π- spectrum, the differences detected between the π+3He and π-3He invariant-mass distributions show that there must be some isospin-one ππ production even at relatively low excess energies. The invariant-mass differences are modeled in terms of the sequential decay N*(1440) -> Delta(1232)π -> Nππ.

nucl-ex↗

arXiv2012

New determination of the mass of the eta meson at COSY-ANKE

A value for the mass of the eta meson has been determined at the COSY-ANKE facility through the measurement of a set of deuteron laboratory beam momenta and associated 3He center-of-mass momenta in the d+p -> 3He+X reaction. The eta was then identified by the missing-mass peak and the production threshold determined. The individual beam momenta were fixed with a relative precision of 3 x 10^-5 for values around 3 GeV/c by using a polarized deuteron beam and inducing an artificial depolarizing spin resonance, which occurs at a well-defined frequency. The final-state momenta in the two-body d+p -> 3He+eta reaction were investigated in detail by studying the size of the 3He momentum ellipse with the forward detection system of the ANKE spectrometer. Final alignment of the spectrometer for this high precision experiment was achieved through a comprehensive study of the 3He final-state momenta as a function of the center-of-mass angles, taking advantage of the full geometrical acceptance. The value obtained for the mass, m(eta)=(547.873 +- 0.005(stat) +- 0.027(syst)) MeV/c^2, is consistent and competitive with other recent measurements, in which the meson was detected through its decay products.

nucl-ex↗

arXiv2008

Lineshape of the Lambda(1405) Hyperon Measured Through its Sigma0 pion0 Decay

The pp -> p K+ Y0 reaction has been studied for hyperon masses m(Y0)<1540 MeV/c2 at COSY-Juelich by using a 3.65 GeV/c circulating proton beam incident on an internal hydrogen target. Final states comprising two protons, one positively charged kaon and one negatively charged pion have been identified with the ANKE spectrometer. Such configurations are sensitive to the production of the ground state Lambda and Sigma0 hyperons as well as the Sigma0(1385) and Lambda(1405) resonances. Applying invariant- and missing-mass techniques, the two overlapping excited states could be well separated, though with limited statistics. The shape and position of the Lambda(1405) distribution, reconstructed cleanly in the Sigma0 pion0 channel, are similar to those found from other decay modes and there is no obvious mass shift. This finding constitutes a challenging test for models that predict Lambda(1405) to be a two-state resonance.

nucl-ex↗

arXiv2006

Study of omega-meson production in pp collisions at ANKE

The production of omega-mesons in the pp->pp omega reaction has been investigated with the COSY-ANKE spectrometer for excess energies of 60 and 92MeV by detecting the two final protons and reconstructing their missing mass. The large multipion background was subtracted using an event-by-event transformation of the proton momenta between the two energies. Differential distributions and total cross sections were obtained after careful studies of possible systematic uncertainties in the overall ANKE acceptance. The results are compared with the predictions of theoretical models. Combined with data on the phi-meson, a more refined estimate is made of the Okubo-Zweig-Iizuka rule violation in the phi/omega production ratio.

nucl-ex↗