Publications (23)60.44 Total impact

Article: Proposed method for laser spectroscopy of pionic helium atoms to determine the chargedpion mass
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ABSTRACT: Metastable pionic helium ($\pi{\rm He}^+$) is a threebody atom composed of a helium nucleus, an electron occupying the $1s$ ground state, and a negatively charged pion $\pi^$ in a Rydberg state with principal and orbital angular momentum quantum numbers of $n\sim \ell+1\sim 16$. We calculate the spinindependent energies of the $\pi{\rm ^3He}^+$ and $\pi{\rm ^4He}^+$ isotopes in the region $n=15$19. These include relativistic and quantum electrodynamics corrections of orders $R_{\infty}\alpha^2$ and $R_{\infty}\alpha^3$ in atomic units, where $R_{\infty}$ and $\alpha$ denote the Rydberg and fine structure constants. The finestructure splitting due to the coupling between the electron spin and the orbital angular momentum of the $\pi^$, and the radiative and Auger decay rates of the states are also calculated. Some states $(n,\ell)=(16,15)$ and $(17,16)$ retain nanosecondscale lifetimes against $\pi^$ absorption into the helium nucleus. We propose to use laser pulses to induce $\pi^$ transitions from these metastable states, to states with large ($\sim 10^{11}$ s$^{1}$) Auger rates. The $\pi{\rm He}^{2+}$ ion that remains after Auger emission of the $1s$ 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 $\pi^$. 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....(continued)04/2014; 
Article: Beam Diagnostics for Measurements of Antiproton Annihilation Cross Sections at Ultralow Energy
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ABSTRACT: The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration of CERN is currently attempting to measure the antiprotonnucleus inflight annihilation cross sections on thin target foils of C, Pd, and Pt at 130 keV of kinetic energy. The lowenergy antiprotons were supplied by the Antiproton Decelerator (AD) and a radiofrequency quadrupole decelerator. For this measurement, a beam profile monitor based on secondary electron emission was developed. Data from this monitor was used to ensure that antiprotons were precisely tuned to the position of an 80mmdiameter experimental target, by measuring the spatial profile of 200nslong beam pulses containing 105  106 antiprotons with an active area of 40 mm × 40 mm and a spatial resolution of 4 mm. By using this monitor, we succeeded in finely tuning antiproton beams on the target, and observed some annihilation events originating from the target.02/2014;  [Show abstract] [Hide abstract]
ABSTRACT: The ASACUSA (Atomic Spectroscopy and Collisions Using Slow Antiprotons) collaboration is currently attempting to observe a laserinduced resonant transition of antiprotonic helium atoms at wavelength of 1154.9 nm. Motivations to observe this transition and a nanosecond nearinfrared laser prepared for this work are presented.02/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Investigating the antiproton cross section on nuclei at low energies (1 eV  1 MeV) is of great interest for fundamental cosmology and nuclear physics as well. The process is of great relevance for the models which try to explain the matter/antimatter asymmetry in the universe assuming the existence of the socalled "island" where antinucleonnucleon annihilations occur in the border region [1]. For the nuclear physics point of view, the annihilation process is considered a useful tool to evaluate the neutron/proton ratio probing the external region of the nucleus. Moreover, the cross section measured at LEAR in the 80s90s showed an unexpected behaviour for energies below 1 MeV. The results showed a saturation with the atomic mass number against the A2/3 trend which is known for higher energies. The ASACUSA collaboration at CERN measured 5.3 MeV antiproton annihilation cross section on different nuclei whose results demonstrated to be consistent with the blackdisk model with the Coulomb correction [2]. So far, experimental limits prevented the data acquisition for energies below 1 MeV. In 2012 the 100 keV region has been investigated for the first time [3]. We present here the results of the experiment.02/2014;  [Show abstract] [Hide abstract]
ABSTRACT: The ASACUSA collaboration of CERN has recently carried out twophoton laser spectroscopy of antiprotonic helium atoms. Three transition frequencies were determined with fractional precisions of 2.35 parts in 109. By comparing the results with threebody QED calculations, the antiprotontoelectron mass ratio was determined as 1836.1526736(23).02/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We review some lasers developed by the ASACUSA collaboration of CERN, to carry out spectroscopy of antiprotonic helium atoms. These lasers were based on the technique of continuouswave injection seeding of pulsed lasers. The laser output covered the wavelength regions 2641154 nm, with peak powers of ~ 1 MW and spectral resolutions of 640 MHz. The devices were recently used to measure the transition frequencies of antiprotonic helium atoms to a fractional precision of several parts in ~ 109.02/2014;  [Show abstract] [Hide abstract]
ABSTRACT: The Atomic Spectroscopy and Collisions Using Slow Antiprotons experiment at the Antiproton Decelerator (AD) facility of CERN constructed segmented scintillators to detect and track the charged pions which emerge from antiproton annihilations in a future superconducting radiofrequency Paul trap for antiprotons. A system of 541 cast and extruded scintillator bars were arranged in 11 detector modules which provided a spatial resolution of 17 mm. Green wavelengthshifting fibers were embedded in the scintillators, and read out by silicon photomultipliers which had a sensitive area of 1 × 1 mm(2). The photoelectron yields of various scintillator configurations were measured using a negative pion beam of momentum p ≈ 1 GeV/c. Various fibers and silicon photomultipliers, fiber end terminations, and couplings between the fibers and scintillators were compared. The detectors were also tested using the antiproton beam of the AD. Nonlinear effects due to the saturation of the silicon photomultiplier were seen at high annihilation rates of the antiprotons.The Review of scientific instruments 02/2014; 85(2):023302. · 1.52 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The resonance transition (n, l) = (40, 36) → (41, 35) of the antiprotonic helium (\overline{{p}}^{4}He+) isotope at a wavelength of 1154.9 nm was detected by laser spectroscopy. The population of \overline{{p}}^{4}He+ occupying the resonance parent state (40, 36) was found to decay at a rate of 0.45 ± 0.04 μs1, which agreed with the theoretical radiative rate of this state. This implied that very few longlived \overline{{p}}^{4}He+ are formed in the higherlying states with principal quantum number n ⩾ 41, in agreement with the results of previous experiments.Journal of Physics B Atomic Molecular and Optical Physics 12/2013; 46(24):5004. · 2.03 Impact Factor 
Article: Twophoton laser spectroscopy of antiprotonic helium and the antiprotontoelectron mass ratio.
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ABSTRACT: Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its particle counterpart. Metastable antiprotonic helium (pHe(+)) is a threebody atom consisting of a normal helium nucleus, an electron in its ground state and an antiproton (p) occupying a Rydberg state with high principal and angular momentum quantum numbers, respectively n and l, such that n ≈ l + 1 ≈ 38. These atoms are amenable to precision laser spectroscopy, the results of which can in principle be used to determine the antiprotontoelectron mass ratio and to constrain the equality between the antiproton and proton charges and masses. Here we report twophoton spectroscopy of antiprotonic helium, in which p(3)He(+) and p(4)He(+) isotopes are irradiated by two counterpropagating laser beams. This excites nonlinear, twophoton transitions of the antiproton of the type (n, l) → (n  2, l  2) at deepultraviolet wavelengths (λ = 139.8, 193.0 and 197.0 nm), which partly cancel the Doppler broadening of the laser resonance caused by the thermal motion of the atoms. The resulting narrow spectral lines allowed us to measure three transition frequencies with fractional precisions of 2.35 parts in 10(9). By comparing the results with threebody quantum electrodynamics calculations, we derived an antiprotontoelectron mass ratio of 1,836.1526736(23), where the parenthetical error represents one standard deviation. This agrees with the protontoelectron value known to a similar precision.Nature 07/2011; 475(7357):4848. · 38.60 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report on the first experimental results for microwave spectroscopy of the hyperfine structure of p¯3He+. Due to the helium nuclear spin, p¯3He+ has a more complex hyperfine structure than p¯4He+, which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the threebody quantum electrodynamics (QED) theory. Two out of four supersuperhyperfine (SSHF) transition lines of the (n,L)=(36,34) state were observed. The measured frequencies of the individual transitions are 11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current theoretical values, but still within their estimated errors. Although the experimental uncertainty for the difference of these frequencies is still very large as compared to that of theory, its measured value agrees with theoretical calculations. This difference is crucial to be determined because it is proportional to the magnetic moment of the antiproton.Physics Letters B 05/2011; 700(1):16. · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In this work we describe the latest results for the measurements of the hyperfine structure of antiprotonic helium3. Two out of four measurable supersuperhyperfine SSHF transition lines of the (n,L)=(36,34) state of antiprotonic helium3 were observed. The measured frequencies of the individual transitions are 11.12548(08) GHz and 11.15793(13) GHz, with an increased precision of about 43% and 25% respectively compared to our first measurements with antiprotonic helium3 [S. Friedreich et al., Phys. Lett. B 700 (2011) 16]. They are less than 0.5 MHz higher with respect to the most recent theoretical values, still within their estimated errors. Although the experimental uncertainty for the difference of 0.03245(15) GHz between these frequencies is large as compared to that of theory, its measured value also agrees with theoretical calculations. The rates for collisions between antiprotonic helium and helium atoms have been assessed through comparison with simulations, resulting in an elastic collision rate of gamma_e = 3.41 + 0.62 MHz and an inelastic collision rate of gamma_i = 0.51 + 0.07 MHz.Journal of Physics B Atomic Molecular and Optical Physics 03/2011; · 2.03 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The spin magnetic moment $\mu^{\overline{p}}_{s}$ of the antiproton can be determined by comparing the measured transition frequencies in $\overline{p}^4$ He + with threebody QED calculations. A comparison between the proton and antiproton can then be used as a test of CPT invariance. The highest measurement precision of the difference between the proton and the antiproton spin magnetic moments to date is 0.3%. A new experimental value of the spin magnetic moment of the antiproton was obtained as $\mu^{\overline{p}}_{s} = 2.7862(83)\mu_{N}$ , slightly better than the previously best measurement. This agrees with $\mu^{p}_{s}$ within 0.24%. In 2009, a new measurement with antiprotonic 3He has been started. A comparison between the theoretical calculations and experimental results would lead to a stronger test of the theory and address systematic errors therein. A measurement of this state will be the first HF measurement on $\overline{p}^3$ He + . We report here on the new experimental setup and the first tests.Hyperfine Interactions 01/2011; 199(13). · 0.21 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report the first measurements of the inelastic spin exchange collision rate between the Hyperfine (HF) levels of antiprotonic helium. We measure the time dependent evolution of the (37, 35) substates to obtain an inelastic collision rate which qualitatively agrees with recent theoretical calculations. We evaluate these results by using the obtained rate as a parameter in a rigorous simulation which we then compare to to previously measured data. We find that our measurement slightly underestimates the collision rate and therefore conclude that the actual value most probably falls within the upper, rather than lower, limit of the error. Comment: 15 pages, 10 figures07/2009;  [Show abstract] [Hide abstract]
ABSTRACT: We report a determination of the antiproton magnetic moment, measured in a threebody system, independent of previous experiments. We present results from a systematic study of the hyperfine (HF) structure of antiprotonic helium where we have achieved a precision more than a factor of 10 better than our first measurement. A comparison between the experimental results and threebody quantum electrodynamic (QED) calculations leads to a new value for the antiproton magnetic moment is 2.7862 (83) nuclear magnetons, which agrees with the magnetic moment of the proton within 2.9 x 10e3.Physics Letters B 05/2009; 678:5559. · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Two detectors which will be used to commission a superconducting radiofrequency Paul trap for antiprotons, now being constructed at CERN and MPQ, are described. One is a microwire secondary electron emission monitor which will nondestructively measure the spatial profile of a low energy (E= 10−100keV) antiproton beam. The other is a system of electromagnetic shower counters which will detect the secondary particles emerging from the antiproton annihilations occurring in the trap.Hyperfine Interactions 04/2009; 194(1):201205. · 0.21 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report a determination of the antiproton magnetic moment, measured in a threebody system, independent of previous experiments. We present results from a systematic study of the hyperfine (HF) structure of antiprotonic helium where we have achieved a precision more than a factor of 10 better than our first measurement. A comparison between the experimental results and threebody quantum electrodynamic (QED) calculations leads to a new value for the antiproton magnetic moment μsp¯=−2.7862(83)μN, which agrees with the magnetic moment of the proton within 2.9×10−3.Physics Letters B 01/2009; 678(1):5559. · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The longitudinal and transverse beam coupling impedance of the first final TOTEM Roman Pot unit has been measured in the laboratory with the wire method. For the evaluation of transverse impedance the wire position has been kept constant, and the insertions of the RP were moved asymmetrically. With the original configuration of the RP, resonances with fairly high Q values were observed. In order to mitigate this problem, RFabsorbing ferrite plates were mounted in appropriate locations. As a result, all resonances were sufficiently damped to meet the stringent LHC beam coupling impedance requirements.07/2008; 
Article: The TOTEM electronics system
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ABSTRACT: TOTEM is an LHC experiment around the same interaction point as CMS. It contains cathode strip chambers (CSC) and gas electron multiplier detectors (GEM) in the CMS cavern and 24 Roman Pots with silicon strip detectors in the LHC tunnel. TOTEM should run both standalone and together with CMS, and should be fully compatible with CMS. All three subdetectors provide level one trigger building signals and use the same chips: VFAT2 providing both tracking data and fast trigger generation signals, the programmable Coincidence Chip, and the LVDS repeater chip. The same counting room hardware receives and handles both trigger building and tracking data.Topical Workshop on Electronics for Particle Physics. 01/2007;  [Show abstract] [Hide abstract]
ABSTRACT: We shall present here the first experimental results for microwave spectroscopy of the hyperfine structure of antiprotonic He3 and a comparison to numerical simulations of the measurement. Due to the helium nuclear spin, antiprotonic He3 has a more complex hyperfine structure than antiprotonic He4 which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the threebody quantum electrodynamics (QED) theory. The comparison of measured data to simulations allows to investigate the collisional processes between the helium atoms of the target medium and the antiprotonic helium atomcules. The collision rates can not be calculated exactly, but estimated by comparison of numeric simulations with the experimental results. Two out of four supersuperhyperfine (SSHF) transition lines of the (n, L) = (36, 34) state were observed. The measured frequencies of the individual transitions are 11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current theoretical values, but still within their estimated errors. The frequency difference between the two lines also agrees with theoretical calculations.Hyperfine Interactions 212(13). · 0.21 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The ASACUSA collaboration has developed injectionseeded Ti:sapphire lasers of linewidth Γpl ∼ 6 MHz, pulse energy 50–100 mJ, and output wavelength λ = 726–941 nm. They are being used in twophoton spectroscopy experiments of antiprotonic helium atoms at the Antiproton Decelerator (AD) of CERN. Ti:sapphire lasers of larger linewidth Γpl ∼ 100 MHz but more robust design will also be used in collinear resonance ionization spectroscopy (CRIS) experiments of neutrondeficient francium ions at the ISOLDE facility.Hyperfine Interactions 212(13). · 0.21 Impact Factor
Publication Stats
33  Citations  
60.44  Total Impact Points  
Top Journals
Institutions

2009–2014

The University of Tokyo
 Department of Physics
Edo, Tōkyō, Japan


2008

The University of Manchester
 School of Physics and Astronomy
Manchester, England, United Kingdom
