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Register a new userUsing stochastic acceleration to place experimental limits on the charge of antihydrogen
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Assuming hydrogen is charge neutral, CPT invariance demands that antihydrogen also be charge neutral. Quantum anomaly cancellation also demands that antihydrogen be charge neutral. Standard techniques based on measurements of macroscopic quantities of atoms cannot be used to measure the charge of antihydrogen. In this paper, we describe how the application of randomly oscillating electric fields to a sample of trapped antihydrogen atoms, a form of stochastic acceleration, can be used to place experimental limits on this charge.
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The ALPHA collaboration has successfully demonstrated the production and the confinement of cold antihydrogen, $overline{mathrm{H}}$. An analysis of trapping data allowed a stringent limit to be placed on the electric charge of the simplest antiatom. Charge neutrality of matter is known to a very high precision, hence a neutrality limit of $overline{mathrm{H}}$ provides a test of CPT invariance. The experimental technique is based on the measurement of the deflection of putatively charged $overline{mathrm{H}}$ in an electric field. The tendency for trapped $overline{mathrm{H}}$ atoms to be displaced by electrostatic fields is measured and compared to the results of a detailed simulation of $overline{mathrm{H}}$ dynamics in the trap. An extensive survey of the systematic errors is performed, with particular attention to those due to the silicon vertex detector, which is the device used to determine the $overline{mathrm{H}}$ annihilation position. The limit obtained on the charge of the $overline{mathrm{H}}$ atom is mbox{$ Q = (-1.3pm1.8pm0.4)times10^{-8}$}, representing the first precision measurement with $overline{mathrm{H}}$.
We study a method to induce resonant transitions between antihydrogen ($bar{H}$) quantum states above a material surface in the gravitational field of the Earth. The method consists of applying a gradient of magnetic field, which is temporally oscillating with the frequency equal to a frequency of transition between gravitational states of antihydrogen. A corresponding resonant change in the spatial density of antihydrogen atoms could be measured as a function of the frequency of applied field. We estimate an accuracy of measuring antihydrogen gravitational states spacing and show how a value of the gravitational mass of the $bar{H}$ atom could be deduced from such a measurement. We also demonstrate that a method of induced transitions could be combined with a free-fall-time measurement in order to further improve the precision.
The antihydrogen programme of the ASACUSA collaboration at the antiproton decelerator of CERN focuses on Rabi-type measurements of the ground-state hyperfine splitting of antihydrogen for a test of the combined Charge-Parity-Time symmetry. The spectroscopy apparatus consists of a microwave cavity to drive hyperfine transitions and a superconducting sextupole magnet for quantum state analysis via Stern-Gerlach separation. However, the small production rates of antihydrogen forestall comprehensive performance studies on the spectroscopy apparatus. For this purpose a hydrogen source and detector have been developed which in conjunction with ASACUSAs hyperfine spectroscopy equipment form a complete Rabi experiment. We report on the formation of a cooled, polarized, and time modulated beam of atomic hydrogen and its detection using a quadrupole mass spectrometer and a lock-in amplification scheme. In addition key features of ASACUSAs hyperfine spectroscopy apparatus are discussed.t
The $^1mathrm{S}_0$-$^3mathrm{P}_0$ clock transition frequency $ u_text{Sr}$ in neutral $^{87}$Sr has been measured relative to the Cs standard by three independent laboratories in Boulder, Paris, and Tokyo over the last three years. The agreement on the $1times 10^{-15}$ level makes $ u_text{Sr}$ the best agreed-upon optical atomic frequency. We combine periodic variations in the $^{87}$Sr clock frequency with $^{199}$Hg$^+$ and H-maser data to test Local Position Invariance by obtaining the strongest limits to date on gravitational-coupling coefficients for the fine-structure constant $alpha$, electron-proton mass ratio $mu$ and light quark mass. Furthermore, after $^{199}$Hg$^+$, $^{171}$Yb$^+$ and H, we add $^{87}$Sr as the fourth optical atomic clock species to enhance constraints on yearly drifts of $alpha$ and $mu$.
Atoms made of a particle and an antiparticle are unstable, usually surviving less than a microsecond. Antihydrogen, made entirely of antiparticles, is believed to be stable, and it is this longevity that holds the promise of precision studies of matter-antimatter symmetry. We have recently demonstrated trapping of antihydrogen atoms by releasing them after a confinement time of 172 ms. A critical question for future studies is: how long can anti-atoms be trapped? Here we report the observation of anti-atom confinement for 1000 s, extending our earlier results by nearly four orders of magnitude. Our calculations indicate that most of the trapped anti-atoms reach the ground state. Further, we report the first measurement of the energy distribution of trapped antihydrogen which, coupled with detailed comparisons with simulations, provides a key tool for the systematic investigation of trapping dynamics. These advances open up a range of experimental possibilities, including precision studies of CPT symmetry and cooling to temperatures where gravitational effects could become apparent.
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