Laser cooling of antihydrogen atoms Baker, C J; Bertsche, W; Capra, A ...
Nature (London),
04/2021, Letnik:
592, Številka:
7852
Journal Article
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The photon-the quantum excitation of the electromagnetic field-is massless but carries momentum. A photon can therefore exert a force on an object upon collision
. Slowing the translational motion of ...atoms and ions by application of such a force
, known as laser cooling, was first demonstrated 40 years ago
. It revolutionized atomic physics over the following decades
, and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen
, the antimatter atom consisting of an antiproton and a positron. By exciting the 1S-2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-α laser radiation
, we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude-with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S-2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic
and gravitational
studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.
The positron, the antiparticle of the electron, predicted by Dirac in 1931 and discovered by Anderson in 1933, plays a key role in many scientific and everyday endeavours. Notably, the positron is a ...constituent of antihydrogen, the only long-lived neutral antimatter bound state that can currently be synthesized at low energy, presenting a prominent system for testing fundamental symmetries with high precision. Here, we report on the use of laser cooled Be
ions to sympathetically cool a large and dense plasma of positrons to directly measured temperatures below 7 K in a Penning trap for antihydrogen synthesis. This will likely herald a significant increase in the amount of antihydrogen available for experimentation, thus facilitating further improvements in studies of fundamental symmetries.
Antiprotons created by laser ionization of antihydrogen are observed to rapidly escape the ALPHA trap. Further, positron plasmas heat more quickly after the trap is illuminated by laser light for ...several hours. These phenomena can be caused by patch potentials-variations in the electrical potential along metal surfaces. A simple model of the effects of patch potentials explains the particle loss, and an experimental technique using trapped electrons is developed for measuring the electric field produced by the patch potentials. The model is validated by controlled experiments and simulations.
The ALPHA Collaboration, based at the CERN Antiproton Decelerator, has recently implemented a novel beamline for low energy (≲100eV) positron and antiproton transport between cylindrical Penning ...traps that have strong axial magnetic fields. Here, we describe how a combination of semianalytical and numerical calculations was used to optimize the layout and design of this beamline. Using experimental measurements taken during the initial commissioning of the instrument, we evaluate its performance and validate the models used for its development. By combining data from a range of sources, we show that the beamline has a high transfer efficiency and estimate that the percentage of particles captured in the experiments from each bunch is(78±3)%for up to105antiprotons and(71±5)%for bunches of up to107positrons.
Background
A philosophical shift in statistics regarding emphasis on “New Statistics” (NS; Cumming, G. (2014). The new statistics: Why and how. Psychological Science, 25(1), 7-29.) over conventional ...null hypothesis significance testing (NHST) raises the question of appropriate material coverage in undergraduate statistics courses.
Objective
We examined current practices in statistics pedagogy at the graduate and undergraduate levels for both NS and NHST.
Method
Using an online survey of a nationwide sample of current graduate students (n = 452) and graduate faculty (n = 162), we examined statistics pedagogy and perceptions of best approaches for teaching undergraduate statistics.
Results
In undergraduate statistics courses, coverage of NS material involves modest instruction in effect sizes and confidence intervals, while NHST remains dominant. Graduate courses have more balanced coverage. Effect size estimation was regarded as the most important NS knowledge for success in graduate school and the topic most in need of increased undergraduate coverage.
Conclusion
Undergraduate statistics courses could increase NS coverage, particularly effect size estimation, to better align with and prepare students for graduate work.
Teaching Implications
This research summarizes graduate program expectations and graduate student experiences regarding undergraduate statistics that current instructors can use to shape the content of their classes.
This research assessed the impact of one night of sleep deprivation on the amplitudes of NREM-sleep event-related potentials (NREM ERPs) and on the frequency of occurrence of related ...electroencephalogram activity including sleep spindles, arousals, K-complexes, and vertex sharp waves (VSWs). The NREM ERPs identified included P220, N350, P450, N550 and P900. During a pre-deprivation night, ten subjects took two 20-min naps separated by a 20-min break at their normal bedtime. Brief tones were presented at three intensity levels (60, 75 and 90 dB) with a 5-s interstimulus interval. Following these naps, subjects were kept awake until their normal bedtime the following day. At that time, they repeated the two-nap procedure. The ERPs obtained for each tone and wake/sleep state for pre- and post-deprivation conditions were analyzed using repeated measures statistical procedures. As anticipated, NREM ERP amplitudes recorded both pre- and post-deprivation increased with tone intensity and with approaching sleep. Also, sleep deprivation was associated with more rapid sleep onset, reduced arousability, and greater spindle production. While sleep deprivation had no effect on the amplitude of P220. Post-deprivation amplitudes of N350, N550 and P900 were greater, especially following the 90-dB tone. There was a corresponding increase in VSWs and K-complexes. These findings are inconsistent with the view that NREM ERPs reflect arousal. The underlying mechanism(s) may facilitate initiation and maintenance of sleep.
Abstract
Introduction
The relationships between maladaptive sleep hygiene with sleep disruption and between sleep disruption and impaired mental health are well established. We suggest sleep hygiene ...behaviors may predict mental health mediated and/or moderated by sleep disruption. Finding these modifiable behaviors are related to mental health will establish a basis for modifying sleep hygiene in efforts to improve well-being.
Methods
Students (N=480) and faculty/staff (N=136) were recruited from the same institution to complete a 45-minute well-being survey in exchange for the chance to win prizes. Within this survey, participants completed measures of positive mental health (the Mental Health Continuum-Short Form; experiences of 10 positive emotions; a 3-item measure of resilience, and a satisfaction with personal relationships rating), negative mental health (the Patient Health Questionnaire-9 for depression; the General Anxiety Disorder-7; and the Perceived Stress Scale), sleep hygiene, and five questions assessing symptoms of inadequate sleep. Measures of mental health and inadequate sleep were correlated with sleep hygiene.
Results
Sleepiness: Poor sleep hygiene was significantly associated with greater sleepiness (students: r(466)=.434; p<.05; faculty/staff: (r(131)=.222; p<.05)). Positive mental health: In students, worse sleep hygiene was significantly associated with poorer overall positive mental health (r(448)=-.35; p<.05), fewer positive emotion experiences (r(449)=-.32; p<.05), lower resilience (r(466)=-.15; p<.05), and lower personal relationship satisfaction (r(468)=-.21; p<.05). The same pattern emerged in faculty/staff as well. Negative mental health: In students, worse sleep hygiene was significantly associated with greater depressive symptoms (r(464)=.49; p<.05), anxiety (r(465)=.41; p<.05), and stress (r(462)=.49; p<.05). Again, this pattern emerged in faculty/staff as well.
Conclusion
We found inadequate sleep hygiene was related to greater sleepiness (indicating more disturbed sleep) and poorer outcomes in measures of positive and negative mental health. Sleep disturbance may influence the strength of, or explain, the relationship between sleep hygiene and mental health status. It has been difficult to demonstrate the importance of sleep hygiene as a target of therapeutic intervention, however, the data presented here suggest an important role for sleep hygiene behaviors in mental status outcomes.
Support (If Any)
Nancy and Craig Wood Odyssey Professorship.
Although, impairments following sleep deprivation have been clearly demonstrated in the literature, researchers have found a wide range of individual variation in response to sleep deprivation. The ...relationship between personality and the subjective and objective impact of sleep deprivation was examined using the Epworth Sleepiness Scale, Stanford Sleepiness Scale, Sleep Hygiene Index, Profile of Mood States, an oddball reaction time test, a multi-task cognitive performance battery (SynWin), and the NEO Personality Inventory Revised. Subjects (14 males, 14 females, mean age 20.5) were sleep deprived for 28–35
h and during this time were allowed access to self-reported typical amounts of tobacco, caffeine, and food. Post sleep deprivation: (a) higher neuroticism scores were related to participants feeling sleepier, experiencing more mood disturbance, and performing inferiorly on a behavioral task; (b) subjects scoring as introverts showed more compromised behavioral performance compared to extraverts. The authors suggest that potential moderating variables of the relationship between personality and sleep deprivation such as stimulant use, food intake, and socialization warrant further investigation.
Abstract
Introduction
One third of participants report that their partner’s sleep problems negatively affect their own sleep (supported by actigraph data). We have previously established that the use ...of bedtime social technology is related to poorer sleep quality and greater sleepiness. Here, we examined the relationship of partner passive social technology use with daytime sleepiness and sleep. Passive social technology use was defined as the potential for sleep interruption by social technology in the absence of user action.
Methods
220 university students (M=20.1 years old, SD=5.6) were recruited from introductory psychology courses and given extra credit for participation. Each participant completed the Sleep Hygiene Index (SHI) with an additional question assessing a partner’s passive technology use: I sleep with my bed partner’s phone sounds or vibrations turned on where I could hear it if I were awake. Participants also completed the Epworth Sleepiness Scale (ESS), the Pittsburg Sleep Quality Index (PSQI), additional questions regarding associated features of inadequate sleep hygiene, and demographic information.
Results
Many students reported frequently or always using bedtime social technology (active: 59.5%; passive: 64.2%) which was significantly related to greater daytime sleepiness (ESS) (r(214)=.219, p<.05), preoccupation with sleep (r(215)=.151, p<.05), mood disturbance (r(214)=.142, p<.05), avolition (r(214)=.188, p<.05), and reduced cognition (r(215)=.138, p<.05). 35.1% reported frequently or always being able to hear a partner’s social technology during bedtime. Frequent passive partner technology use was significantly related to greater daytime sleepiness (ESS) (r(211)=.149, p<.05) and poorer sleep efficiency (r(204)=-.153, p<.05). The addition of social technology questions strengthened the predictive ability of the SHI for daytime sleepiness (from r=.295 to r=.350).
Conclusion
Participants were found to be frequent users of bedtime social technology leading to disrupted sleep and increased sleepiness. One third of participants reported passive bed partner social technology use and this was also found to be related to disrupted sleep and increased sleepiness. Adding social technology use strengthened the SHI’s predictive ability for daytime sleepiness. Future research should investigate whether bed partner active social technology use similarly disrupts sleep.
Support (If Any)
None.
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