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Masaki Hori - One of the best experts on this subject based on the ideXlab platform.
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laser spectroscopy measurements of metastable pionic Helium Atoms at paul scherrer institute
Few-body Systems, 2021Co-Authors: Masaki Hori, Andreas Dax, Anna Sótér, Hossein Aghaikhozani, Daniel BarnaAbstract:We review recent experiments carried out by the PiHe collaboration of the Paul Scherrer Institute (PSI) that observed an infrared transition of three-body pionic Helium Atoms by laser spectroscopy. These measurements may lead to a precise determination of the charged pion mass, and complement experiments of antiprotonic Helium Atoms carried out at the new ELENA facility of CERN.
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Laser spectroscopy of pionic Helium Atoms
Nature, 2020Co-Authors: Masaki Hori, Andreas Dax, Hossein Aghai-khozani, Anna Sótér, Daniel BarnaAbstract:Long-lived pionic Helium Atoms (composed of a Helium-4 nucleus, an electron and a negatively charged pion) are synthesized in a superfluid-Helium target, as confirmed by laser spectroscopy involving the pion-occupied orbitals. Charged pions^ 1 are the lightest and longest-lived mesons. Mesonic Atoms are formed when an orbital electron in an atom is replaced by a negatively charged meson. Laser spectroscopy of these Atoms should permit the mass and other properties of the meson to be determined with high precision and could place upper limits on exotic forces involving mesons (as has been done in other experiments on antiprotons^ 2 – 9 ). Determining the mass of the π ^− meson in particular could help to place direct experimental constraints on the mass of the muon antineutrino^ 10 – 13 . However, laser excitations of mesonic Atoms have not been previously achieved because of the small number of Atoms that can be synthesized and their typically short (less than one picosecond) lifetimes against absorption of the mesons into the nuclei^ 1 . Metastable pionic Helium ( π ^4He^+) is a hypothetical^ 14 – 16 three-body atom composed of a Helium-4 nucleus, an electron and a π ^− occupying a Rydberg state of large principal ( n ≈ 16) and orbital angular momentum ( l ≈ n − 1) quantum numbers. The π ^4He^+ atom is predicted to have an anomalously long nanosecond-scale lifetime, which could allow laser spectroscopy to be carried out^ 17 . Its atomic structure is unique owing to the absence of hyperfine interactions^ 18 , 19 between the spin-0 π ^ − and the ^ 4 He nucleus. Here we synthesize π ^4He^+ in a superfluid-Helium target and excite the transition ( n , l ) = (17, 16) → (17, 15) of the π ^ − -occupied π ^4He^+ orbital at a near-infrared resonance frequency of 183,760 gigahertz. The laser initiates electromagnetic cascade processes that end with the nucleus absorbing the π ^ − and undergoing fission^ 20 , 21 . The detection of emerging neutron, proton and deuteron fragments signals the laser-induced resonance in the atom, thereby confirming the presence of π ^4He^+. This work enables the use of the experimental techniques of quantum optics to study a meson.
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method for laser spectroscopy of metastable pionic Helium Atoms
Hyperfine Interactions, 2015Co-Authors: Masaki Hori, Anna Sótér, Daniel Barna, Hossein Aghaikhozani, R S Hayano, Y Murakami, Hiroyuki YamadaAbstract:The PiHe collaboration is currently attempting to carry out laser spectroscopy of metastable pionic Helium Atoms using the high-intensity π− beam of the ring cyclotron facility of the Paul Scherrer Institute. These Atoms are heretofore hypothetical three-body Coulomb systems each composed of a Helium nucleus, a π− occupying a Rydberg state, and an electron occupying the 1s ground state. We briefly review the proposed method by which we intend to detect the laser spectroscopic signal. This complements our experiments on metastable antiprotonic Helium Atoms at CERN.
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Two photon laser spectroscopy of antiprotonic Helium Atoms at CERN’s AD
Hyperfine Interactions, 2014Co-Authors: Masaki HoriAbstract:The ASACUSA collaboration of CERN has carried out two-photon laser spectroscopy of antiprotonic Helium Atoms using counter-propagating ultraviolet laser beams. This excited some non-linear transitions of the antiproton at the wavelengths λ = 139.8–197.0 nm, in a way that reduced the thermal Doppler broadening of the observed resonances. The resulting narrow spectral lines allowed the measurement of three transition frequencies with fractional precisions of 2.3–5 parts in 10^9. By comparing these values with three-body QED calculations, the antiproton-to-electron mass ratio was derived as 1836.1526736(23). We briefly review these results.
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proposed method for laser spectroscopy of pionic Helium Atoms to determine the charged pion mass
Physical Review A, 2014Co-Authors: Masaki Hori, Anna Sótér, V I KorobovAbstract:Metastable pionic Helium ($\ensuremath{\pi}{\mathrm{He}}^{+}$) is a three-body atom composed of a Helium nucleus, an electron occupying the 1$s$ ground state, and a negatively charged pion ${\ensuremath{\pi}}^{\ensuremath{-}}$ in a Rydberg state with principal and orbital angular momentum quantum numbers of $n\ensuremath{\sim}\ensuremath{\ell}+1\ensuremath{\sim}16$. We calculate the spin-independent energies of the $\ensuremath{\pi}\phantom{\rule{0.16em}{0ex}}{{}^{3}\mathrm{He}}^{+}$ and $\ensuremath{\pi}\phantom{\rule{0.16em}{0ex}}{{}^{4}\mathrm{He}}^{+}$ isotopes in the region $n=15$--19. These include relativistic and quantum electrodynamics corrections of orders ${R}_{\ensuremath{\infty}}{\ensuremath{\alpha}}^{2}$ and ${R}_{\ensuremath{\infty}}{\ensuremath{\alpha}}^{3}$ in atomic units, where ${R}_{\ensuremath{\infty}}$ and $\ensuremath{\alpha}$ denote the Rydberg and fine structure constants. The fine-structure splitting due to the coupling between the electron spin and the orbital angular momentum of the ${\ensuremath{\pi}}^{\ensuremath{-}}$ and the radiative and Auger decay rates of the states are also calculated. Some states $(n,\ensuremath{\ell})=(16,15)$ and $(17,16)$ retain nanosecond-scale lifetimes against ${\ensuremath{\pi}}^{\ensuremath{-}}$ absorption into the Helium nucleus. We propose the use of laser pulses to induce ${\ensuremath{\pi}}^{\ensuremath{-}}$ transitions from these metastable states to states with large ($\ensuremath{\sim}{10}^{11}$ s${}^{\ensuremath{-}1}$) Auger rates. The $\ensuremath{\pi}{\mathrm{He}}^{2+}$ ion that remains after Auger emission of the 1$s$ electron undergoes Stark mixing with the $s$, $p$, and $d$ states during collisions with the Helium Atoms in the experimental target. This leads to immediate nuclear absorption of the ${\ensuremath{\pi}}^{\ensuremath{-}}$. The resonance condition between the laser beam and the atom is thus revealed as a sharp spike in the rates of neutrons, protons, deuterons, and tritons that emerge. A resonance curve is obtained from which the $\ensuremath{\pi}{\mathrm{He}}^{+}$ transition frequency can in principle be determined with a fractional precision of ${10}^{\ensuremath{-}8}--{10}^{\ensuremath{-}6}$ provided the systematic uncertainties can be controlled. By comparing the measured $\ensuremath{\pi}{\mathrm{He}}^{+}$ frequencies with the calculated values, the ${\ensuremath{\pi}}^{\ensuremath{-}}$ mass may be determined with a similar precision. The $\ensuremath{\pi}{\mathrm{He}}^{+}$ will be synthesized by allowing a high-intensity ($g{10}^{8}$ s${}^{\ensuremath{-}1}$) beam of ${\ensuremath{\pi}}^{\ensuremath{-}}$produced by a cyclotron to come to rest in a Helium target. The precise time structure of the ${\ensuremath{\pi}}^{\ensuremath{-}}$ beam is used to ensure a sufficient rate of coincidence between the resonant laser pulses and the $\ensuremath{\pi}{\mathrm{He}}^{+}$ Atoms.
R S Hayano - One of the best experts on this subject based on the ideXlab platform.
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Effects of impurity molecules on the lifetime of antiprotonic Helium Atoms
2020Co-Authors: Juh B A Asz, R S Hayano, E Widmann, J Eades, M Hori, D Horv, T Ishikawa, H A Torii, H Yamaguchi, T YamazakiAbstract:Abstract Quenching of metastable antiprotonic Helium Atoms in collisions with hydrogen and deuterium molecules has been studied using laser spectroscopy at CERNÕs antiproton decelerator. The temperature dependence of the quenching cross sections of the antiprotonic states ðn; lÞ ¼ ð37; 34Þ, ð38; 35Þ and ð38; 37Þ has been investigated and a deviation from the Arrhenius law was found at low temperatures. In case of the state ð38; 37Þ with deuterium, detailed measurements revealed that the quenching cross section levels off at low temperatures indicating a strong quantum tunneling effect. Ó 2003 Elsevier B.V. All rights reserved. PACS: 36.10.)k; 34.20.Gj; 82.20.Xr Keywords: Quantum tunneling; Antiprotonic Helium; Hydrogen; Deuterium; Temperature dependence of quenching cross section An antiprotonic Helium atom is an exotic three-body system consisting of an antiproton, an electron and a Helium nucleus ( p pHe þ p p À e À À He 2þ ). Various properties of these Atoms (transition energies, state lifetimes etc.) have been extensively studied in the past years using a laser spectroscopy method According to the theoretical calculations of Sauge and Valiron, an ðn; lÞ-dependent activation barrier exists for this kind of reaction which could explain the observed quenching behaviour where r 0 is the cross section at infinitely high temperatures (this we expect to be close to the geometrical cross section), E b is the height of the activation barrier, k is the Boltzmann constant and T is the temperature. However, all previous measurements of quenching by hydrogen and deuterium molecules were done at 30 K; therefore in 2002 we measured the quenching cross sections of three metastable antiprotonic states at higher temperatures to test the above temperature dependence and possibly determine the reaction barrier heights. These measurements, together with the theoretical calculations, can give us a better understanding of the physico-chemistry of cold interstellar and protostellar clouds where similar low temperature reactions play a significant role, especially various hydrogen/deuterium fractionation processes that cause enrichment of deuterium in these environments. The quenching cross section of a metastable antiprotonic state can be obtained by measuring the decay rate of the state at different impurity concentrations using laser spectroscopy. Assuming that the antiprotonic Helium Atoms are quenched in binary collisions with the impurity molecules, the decay rate cðn; lÞ of the state then can be expressed as cðn; lÞ ¼ c 0 ðn; lÞ þ n imp v th r q ðn; lÞ; ð2Þ where c 0 ðn; lÞ is the ÔintrinsicÕ decay rate of the state in pure Helium which can be calculated theoretically, n imp is the number density of the impurity molecules, is the relative velocity of the colliding molecules The decay rate of a metastable state can be measured using two methods which are based on the same laser spectroscopy method. Antiprotonic states can be either long-lived metastable states from where antiprotons can de-excite to lowerlying states by emitting a photon, or short-lived states from where antiprotons annihilate on the Helium nucleus. Due to this difference in the lifetime, short-lived states have very small antiproton population compared to long-lived states. Antiprotons in a long-lived metastable state can be efficiently stimulated by a laser pulse to make a transition to a short-lived state if we choose a transition that satisfies the rules Dn ¼ AE1 and Dl ¼ AE1. Under such conditions, a laser pulse tuned to a metastable-to-short-lived transition and fired into the target containing p pHe þ Atoms will produce a peak in the annihilation time spectrum of the antiprotons, since it suddenly increases the population of the short-lived state. If the state whose quenching cross section we want to measure can be the parent state of such a metastable-toshort-lived laser-induced transition, then the decay rate c of the state can be obtained in the following way. We measure the area of the laser-induced peak in the antiproton annihilation time spectrum (normalized to the total background) at different laser firing times. Since the area of the peak is proportional to the population of the parent state at the time of the laser firing, this way we obtain the population lifetime s p of the parent state. If feeding to this state from upper states is negligible, then the inverse of this lifetime is equal to the decay rate of the state: c ¼ 1=s p . This is the Ôt1-scanÕ method If the state is not accessible with an ordinary laser-induced transition described above, the hydrogen-assisted inverse resonance (HAIR) or deuterium-assisted inverse resonance (DAIR) methods can be used Our gas target consisted of 4 He to which hydrogen or deuterium was premixed at molar concentrations of 30-10,000 ppm. We used a cryogenic target chamber for the measurements between 25 and 100 K, and another target chamber with a larger target volume for the room temperature measurements. Both chambers have a stainless steel window on the upstream wall for the antiproton beam, and a quartz window on the downstream wall for the laser beam. The temperature of the cryogenic target was measured with a silicon diode sensor with an uncertainty of 1 K. The temperature of the room temperature target was not measured directly so an uncertainty of 2 K was assigned in these cases. The absolute number density of the H 2 and D 2 molecules was varied not only by changing gas mixture but also by changing the pressure of the gas target between 1 and 8 bar. Although increasing pressure decreases the lifetime of metastable states, this effect is negligible compared to the lifetime shortening caused by the increasing density of the H 2 and D 2 molecules We determined the decay rates of the following metastable antiprotonic states: ðn; lÞ ¼ ð37; 34Þ with hydrogen and deuterium using the transition ð37; 34Þ ! ð36; 33Þ with the t1-scan method, ð38; 35Þ with hydrogen and deuterium using the transition ð37; 34Þ ! ð38; 35Þ with the HAIR/ DAIR method, and ð38; 37Þ with hydrogen and deuterium using the transition ð37; 36Þ ! ð38; 37Þ with the HAIR/DAIR method. If the decay rates measured at a given temperature and for a given antiprotonic state and the theoretically calculated decay rate in pure Helium (i.e. at n imp ¼ 0) where r t is independent of the temperature. The term r t in Eq. (3) is most likely related to the quantum tunneling of the colliding molecule through the activation barrier, as suggested by Sauge and Valiron The geometrical cross section of the D 2 -He collision is 21 · 10 À16 cm
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method for laser spectroscopy of metastable pionic Helium Atoms
Hyperfine Interactions, 2015Co-Authors: Masaki Hori, Anna Sótér, Daniel Barna, Hossein Aghaikhozani, R S Hayano, Y Murakami, Hiroyuki YamadaAbstract:The PiHe collaboration is currently attempting to carry out laser spectroscopy of metastable pionic Helium Atoms using the high-intensity π− beam of the ring cyclotron facility of the Paul Scherrer Institute. These Atoms are heretofore hypothetical three-body Coulomb systems each composed of a Helium nucleus, a π− occupying a Rydberg state, and an electron occupying the 1s ground state. We briefly review the proposed method by which we intend to detect the laser spectroscopic signal. This complements our experiments on metastable antiprotonic Helium Atoms at CERN.
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near infrared laser spectroscopy of antiprotonic Helium Atoms
2013 International Nuclear Physics Conference INPC 2013, 2014Co-Authors: Takumi Kobayashi, Andreas Dax, Daniel Barna, R S Hayano, Y Murakami, K Todoroki, Hideaki Yamada, L Venturelli, N ZurloAbstract:The ASACUSA (Atomic Spectroscopy and Collisions Using Slow Antipro- tons) collaboration is currently attempting to observe a laser-induced resonant transition of antiprotonic Helium Atoms at wavelength of 1154.9 nm. Motivations to observe this transition and a nanosecond near-infrared laser prepared for this work are presented.
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antiproton to electron mass ratio determined by two photon laser spectroscopy of antiprotonic Helium Atoms
2013 International Nuclear Physics Conference INPC 2013, 2014Co-Authors: Anna Sótér, Masaki Hori, Andreas Dax, Daniel Barna, R S Hayano, E Widmann, S Friedreich, B Juhasz, T Pask, D HorvathAbstract:The ASACUSA collaboration of CERN has recently carried out two-photon laser spectroscopy of antiprotonic Helium Atoms. Three transition frequencies were de- termined with fractional precisions of 2.3-5 parts in 10 9 . By comparing the results with three-body QED calculations, the antiproton-to-electron mass ratio was determined as 1836.1526736(23).
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kaonic Helium Atoms
Hyperfine Interactions, 2009Co-Authors: R S HayanoAbstract:Recent progress on the x-ray spectroscopy of kaonic Helium Atoms as well as on the precision laser spectroscopy of antiprotonic Helium Atoms are presented. Some historical background connecting these two exotic Helium Atoms is also discussed.
W Vassen - One of the best experts on this subject based on the ideXlab platform.
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simultaneous magneto optical trapping of a boson fermion mixture of metastable Helium Atoms
Physical Review Letters, 2004Co-Authors: R J W Stas, W Hogervorst, J M Mcnamara, W VassenAbstract:We simultaneously confine fermionic metastable $^{3}\mathrm{H}\mathrm{e}$ Atoms and bosonic metastable $^{4}\mathrm{H}\mathrm{e}$ Atoms in a magneto-optical trap. The trapped clouds, containing up to $1.5\ifmmode\times\else\texttimes\fi{}{10}^{8}$ Atoms of each isotope, are characterized by measuring ions and metastable Helium Atoms escaping from the trap. Optical pumping of $^{3}\mathrm{H}\mathrm{e}$ Atoms to a nontrapped hyperfine state is investigated and it is shown that large atom numbers can be confined without additional repumping lasers. Unique possibilities for quantum degeneracy experiments with mixtures of spin-polarized metastable $^{3}\mathrm{H}\mathrm{e}$ and $^{4}\mathrm{H}\mathrm{e}$ Atoms are indicated.
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large numbers of cold metastable Helium Atoms in a magneto optical trap
Physical Review A, 1999Co-Authors: Norbert Herschbach, Eric A Hessels, W Hogervorst, W VassenAbstract:We report loading of 1.5310 metastable triplet Helium Atoms in a large magneto-optical trap, using far-red-detuned laser beams. We fully characterized this trap by measuring trap losses and absorption of a probe beam. From the highly nonexponential trap decay we derive Penning ionization loss rate coefficients for two detunings: 5.3(9)310 cm/s at 235 MHz and 3.7(6)310 cm/s at 244 MHz. Also, we find that the loss rate is maximum at 25 MHz detuning, where the rate is 1.3(3)310 cm/s, much larger than recent theoretical and experimental values. In the absence of light the S-S ionization rate constant is measured to be 1.3(2)310 cm/s. @S1050-2947~99!51408-X#
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large numbers of cold metastable Helium Atoms in a magneto optical trap
Physical Review A, 1999Co-Authors: Paul Tol, Norbert Herschbach, Eric A Hessels, W Hogervorst, W VassenAbstract:We report loading of $1.5\ifmmode\times\else\texttimes\fi{}{10}^{9}$ metastable triplet Helium Atoms in a large magneto-optical trap, using far-red-detuned laser beams. We fully characterized this trap by measuring trap losses and absorption of a probe beam. From the highly nonexponential trap decay we derive Penning ionization loss rate coefficients for two detunings: $5.3(9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}{\mathrm{cm}}^{3}/\mathrm{s}$ at $\ensuremath{-}35\mathrm{MHz}$ and $3.7(6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}{\mathrm{cm}}^{3}/\mathrm{s}$ at $\ensuremath{-}44\mathrm{MHz}.$ Also, we find that the loss rate is maximum at $\ensuremath{-}5\mathrm{MHz}$ detuning, where the rate is $1.3(3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}{\mathrm{cm}}^{3}/\mathrm{s},$ much larger than recent theoretical and experimental values. In the absence of light the $S\ensuremath{-}S$ ionization rate constant is measured to be $1.3(2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}{\mathrm{cm}}^{3}/\mathrm{s}.$
F J Hartmann - One of the best experts on this subject based on the ideXlab platform.
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laser measurements of the density shifts of resonance lines in antiprotonic Helium Atoms and stringent constraint on the antiproton charge and mass
Physical Review A, 1999Co-Authors: H Torii, Masaki Hori, T Yamazaki, R S Hayano, N Morita, M Kumakura, I Sugai, B Ketzer, T Ishikawa, F J HartmannAbstract:We have performed laser spectroscopy of metastable antiprotonic Helium Atoms ( pHe) formed in Helium media of 0.2–8.0 bars at 5.8–6.3 K and have observed a density dependence of the resonance vacuum wavelengths for the known transitions (n ,l)5(39,35)→(38,34) and (37,34)→(36,33). They showed linear redshifts of 0.6160.01 GHz and 0.2260.02 GHz per 1 g/l, respectively. With the shift parameters above, the transition vacuum wavelengths were extrapolated to zero-density limits, yielding l05597.257060.0003 nm and l05470.722060.0006 nm, respectively. These values, with a 0.5-ppm precision, were compared with the result of recent theoretical calculations on the energy of the Coulombic three-body system, including relativistic corrections and the Lamb shift. The agreement between our experimental values and the calculations has become as good as 2310. This excellent agreement in turn provides a precise value of the antiproton Rydberg constant that surpasses the currently known precision and sets a severe constraint on the antiproton charge (2Qp) and the mass (M p) that both uQp2Qpu/e and uM p2M pu/M p be less than 5310, when a more precisely known constraint on the charge-to-mass ratio is combined. Thus we have opened a possibility of determining fundamental constants of the antiproton. @S1050-2947~99!04501-1#
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laser measurements of the density shifts of resonance lines in antiprotonic Helium Atoms and stringent constraint on the antiproton charge and mass
Physical Review A, 1999Co-Authors: H Torii, Masaki Hori, T Yamazaki, R S Hayano, N Morita, M Kumakura, I Sugai, B Ketzer, Takuji Ishikawa, F J HartmannAbstract:We have performed laser spectroscopy of metastable antiprotonic Helium Atoms $(\overline{p}{\mathrm{He}}^{+})$ formed in Helium media of 0.2--8.0 bars at 5.8--6.3 K and have observed a density dependence of the resonance vacuum wavelengths for the known transitions $(n,l)=(39,35)\ensuremath{\rightarrow}(38,34)$ and $(37,34)\ensuremath{\rightarrow}(36,33).$ They showed linear redshifts of $0.61\ifmmode\pm\else\textpm\fi{}0.01$ GHz and $0.22\ifmmode\pm\else\textpm\fi{}0.02$ GHz per 1 g/l, respectively. With the shift parameters above, the transition vacuum wavelengths were extrapolated to zero-density limits, yielding ${\ensuremath{\lambda}}_{0}=597.2570\ifmmode\pm\else\textpm\fi{}0.0003$ nm and ${\ensuremath{\lambda}}_{0}=470.7220\ifmmode\pm\else\textpm\fi{}0.0006$ nm, respectively. These values, with a 0.5-ppm precision, were compared with the result of recent theoretical calculations on the energy of the Coulombic three-body system, including relativistic corrections and the Lamb shift. The agreement between our experimental values and the calculations has become as good as $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}.$ This excellent agreement in turn provides a precise value of the antiproton Rydberg constant that surpasses the currently known precision and sets a severe constraint on the antiproton charge $(\ensuremath{-}{Q}_{\overline{p}})$ and the mass ${(M}_{\overline{p}})$ that both $|{Q}_{\mathit{p}}\ensuremath{-}{Q}_{\overline{p}}|/e$ and $|{M}_{\mathit{p}}\ensuremath{-}{M}_{\overline{p}}|{/M}_{p}$ be less than $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7},$ when a more precisely known constraint on the charge-to-mass ratio is combined. Thus we have opened a possibility of determining fundamental constants of the antiproton.
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isotope effects on delayed annihilation time spectra of antiprotonic Helium Atoms in a low temperature gas
Physical Review A, 1996Co-Authors: B Ketzer, I Sugai, F J Hartmann, Toshimitsu Yamazaki, H. Daniel, T Von Egidy, A Niestroj, S Schmid, W Schmid, K NakayoshiAbstract:The delayed annihilation time spectra (DATS) of antiprotonic Helium Atoms have been studied in isotopically pure low-temperature $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$ gas at various densities. The DATS taken at 5.8 K and 400 mbar are very similar in shape except for (i) a small difference in the time scale and (ii) the presence of a distinct fast decay component in the case of $^{3}\mathrm{He}$. The ratio of overall trapping times (mean lifetimes against annihilation), R=${\mathit{T}}_{\mathrm{trap}}$${(}^{4}$He)/${\mathit{T}}_{\mathrm{trap}}$${(}^{3}$He), has been determined to be 1.144 \ifmmode\pm\else\textpm\fi{} 0.009, which is in good agreement with a theoretical estimate yielding R=[${\mathit{M}}^{\mathrm{*}}$(p\ifmmode\bar\else\textasciimacron\fi{}${\mathrm{}}^{4}$He)/ ${\mathit{M}}^{\mathrm{*}}$(p\ifmmode\bar\else\textasciimacron\fi{}${\mathrm{}}^{3}$He)${]}^{2}$=1.14, where ${\mathit{M}}^{\mathrm{*}}$ denotes the reduced mass of the p\ifmmode\bar\else\textasciimacron\fi{}${\mathrm{He}}^{2+}$system. The presence of a short-lived component with a lifetime of 0.154\ifmmode\pm\else\textpm\fi{}0.007 \ensuremath{\mu}s in the case of $^{3}\mathrm{He}$ suggests that the p\ifmmode\bar\else\textasciimacron\fi{}${\mathrm{}}^{3}$${\mathrm{He}}^{+}$atom has a state of intermediate lifetime on the border between a metastable zone and an Auger-dominated short-lived zone. The fraction of antiprotons trapped in metastable states at 5.8 K and 400 mbar is lower by 22.2(4)% for $^{3}\mathrm{than}$ for $^{4}\mathrm{He}$. All the data can be fitted fairly well with simple three-level and four-level cascade models. \textcopyright{} 1996 The American Physical Society.
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first observation of laser induced resonant annihilation in metastable antiprotonic Helium Atoms
Physical Review Letters, 1994Co-Authors: N Morita, T Yamazaki, R S Hayano, M Kumakura, E Widmann, H Masuda, I Sugai, F E Maas, H Torii, F J HartmannAbstract:We have observed the first laser-induced resonant transitions in antiprotonic Helium Atoms. These occur between metastable states and Auger dominated short lived states, and show that the anomalous longevity of antiprotons previously observed in Helium media results from the formation of high-n high-l atomic states of p\ifmmode\bar\else\textasciimacron\fi{}${\mathrm{He}}^{+}$. The observed transition with vacuum wavelength 597.259\ifmmode\pm\else\textpm\fi{}0.002 nm is tentatively assigned to (n,l)=(39,35)\ensuremath{\rightarrow}(38,34).
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Formation of long-lived gas-phase antiprotonic Helium Atoms and quenching by H2
Nature, 1993Co-Authors: Toshimitsu Yamazaki, R S Hayano, F J Hartmann, Eberhard Widmann, Motoki Iwasaki, Satoshi N. Nakamura, K. Shigaki, H. Daniel, T. Von Egidy, P. HofmannAbstract:IN 1964 Condo1 suggested that the decay characteristics of negative (π− and K−) mesons in Helium bubble chambers could be explained by the capture of these particles in large-angular-momentum meta-stable orbitals of exotic Helium Atoms. Russell2 predicted that similar "Atoms' might be formed by antiprotons in liquid Helium. Nearly two decades later the postulated metastability of K− and π− mesons in liquid Helium was observed experimentally3–5. We recently observed6 that about 3% of the antiprotons stopped in liquid Helium survive for several microseconds before annihilating in the Helium nuclei. This is more than a million times longer than the typical (picosecond) lifetimes of antiprotons that come to rest in matter, and it represents the signature of the formation of metastable antiprotonic Atoms. Here we show that the same phenomenon is observed in gas-phase Helium, but that surprisingly the lifetime of the 'Atoms' is the same as in the liquid phase, despite the reduction in collisional de-excitation. In addition, we show that the presence of trace amounts of hydrogen gas greatly reduces the lifetime, suggesting that a single collision with H2 is sufficient to destroy the metastability.
Daniel Barna - One of the best experts on this subject based on the ideXlab platform.
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laser spectroscopy measurements of metastable pionic Helium Atoms at paul scherrer institute
Few-body Systems, 2021Co-Authors: Masaki Hori, Andreas Dax, Anna Sótér, Hossein Aghaikhozani, Daniel BarnaAbstract:We review recent experiments carried out by the PiHe collaboration of the Paul Scherrer Institute (PSI) that observed an infrared transition of three-body pionic Helium Atoms by laser spectroscopy. These measurements may lead to a precise determination of the charged pion mass, and complement experiments of antiprotonic Helium Atoms carried out at the new ELENA facility of CERN.
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Laser spectroscopy of pionic Helium Atoms
Nature, 2020Co-Authors: Masaki Hori, Andreas Dax, Hossein Aghai-khozani, Anna Sótér, Daniel BarnaAbstract:Long-lived pionic Helium Atoms (composed of a Helium-4 nucleus, an electron and a negatively charged pion) are synthesized in a superfluid-Helium target, as confirmed by laser spectroscopy involving the pion-occupied orbitals. Charged pions^ 1 are the lightest and longest-lived mesons. Mesonic Atoms are formed when an orbital electron in an atom is replaced by a negatively charged meson. Laser spectroscopy of these Atoms should permit the mass and other properties of the meson to be determined with high precision and could place upper limits on exotic forces involving mesons (as has been done in other experiments on antiprotons^ 2 – 9 ). Determining the mass of the π ^− meson in particular could help to place direct experimental constraints on the mass of the muon antineutrino^ 10 – 13 . However, laser excitations of mesonic Atoms have not been previously achieved because of the small number of Atoms that can be synthesized and their typically short (less than one picosecond) lifetimes against absorption of the mesons into the nuclei^ 1 . Metastable pionic Helium ( π ^4He^+) is a hypothetical^ 14 – 16 three-body atom composed of a Helium-4 nucleus, an electron and a π ^− occupying a Rydberg state of large principal ( n ≈ 16) and orbital angular momentum ( l ≈ n − 1) quantum numbers. The π ^4He^+ atom is predicted to have an anomalously long nanosecond-scale lifetime, which could allow laser spectroscopy to be carried out^ 17 . Its atomic structure is unique owing to the absence of hyperfine interactions^ 18 , 19 between the spin-0 π ^ − and the ^ 4 He nucleus. Here we synthesize π ^4He^+ in a superfluid-Helium target and excite the transition ( n , l ) = (17, 16) → (17, 15) of the π ^ − -occupied π ^4He^+ orbital at a near-infrared resonance frequency of 183,760 gigahertz. The laser initiates electromagnetic cascade processes that end with the nucleus absorbing the π ^ − and undergoing fission^ 20 , 21 . The detection of emerging neutron, proton and deuteron fragments signals the laser-induced resonance in the atom, thereby confirming the presence of π ^4He^+. This work enables the use of the experimental techniques of quantum optics to study a meson.
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method for laser spectroscopy of metastable pionic Helium Atoms
Hyperfine Interactions, 2015Co-Authors: Masaki Hori, Anna Sótér, Daniel Barna, Hossein Aghaikhozani, R S Hayano, Y Murakami, Hiroyuki YamadaAbstract:The PiHe collaboration is currently attempting to carry out laser spectroscopy of metastable pionic Helium Atoms using the high-intensity π− beam of the ring cyclotron facility of the Paul Scherrer Institute. These Atoms are heretofore hypothetical three-body Coulomb systems each composed of a Helium nucleus, a π− occupying a Rydberg state, and an electron occupying the 1s ground state. We briefly review the proposed method by which we intend to detect the laser spectroscopic signal. This complements our experiments on metastable antiprotonic Helium Atoms at CERN.
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near infrared laser spectroscopy of antiprotonic Helium Atoms
2013 International Nuclear Physics Conference INPC 2013, 2014Co-Authors: Takumi Kobayashi, Andreas Dax, Daniel Barna, R S Hayano, Y Murakami, K Todoroki, Hideaki Yamada, L Venturelli, N ZurloAbstract:The ASACUSA (Atomic Spectroscopy and Collisions Using Slow Antipro- tons) collaboration is currently attempting to observe a laser-induced resonant transition of antiprotonic Helium Atoms at wavelength of 1154.9 nm. Motivations to observe this transition and a nanosecond near-infrared laser prepared for this work are presented.
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antiproton to electron mass ratio determined by two photon laser spectroscopy of antiprotonic Helium Atoms
2013 International Nuclear Physics Conference INPC 2013, 2014Co-Authors: Anna Sótér, Masaki Hori, Andreas Dax, Daniel Barna, R S Hayano, E Widmann, S Friedreich, B Juhasz, T Pask, D HorvathAbstract:The ASACUSA collaboration of CERN has recently carried out two-photon laser spectroscopy of antiprotonic Helium Atoms. Three transition frequencies were de- termined with fractional precisions of 2.3-5 parts in 10 9 . By comparing the results with three-body QED calculations, the antiproton-to-electron mass ratio was determined as 1836.1526736(23).