A 16-parts-per-trillion measurement of the antiproton-to-proton charge-mass ratio.

The standard model of particle physics is both incredibly successful and glaringly incomplete. Among the questions left open is the striking imbalance of matter and antimatter in the observable universe1, which inspires experiments to compare the fundamental properties of matter/antimatter conjugates with high precision2-5. Our experiments deal with direct investigations of the fundamental properties of protons and antiprotons, performing spectroscopy in advanced cryogenic Penning trap systems6. For instance, we previously compared the proton/antiproton magnetic moments with 1.5 parts per billion fractional precision7,8, which improved upon previous best measurements9 by a factor of greater than 3,000. Here we report on a new comparison of the proton/antiproton charge-to-mass ratios with a fractional uncertainty of 16 parts per trillion. Our result is based on the combination of four independent long-term studies, recorded in a total time span of 1.5 years. We use different measurement methods and experimental set-ups incorporating different systematic effects. The final result, [Formula: see text], is consistent with the fundamental charge-parity-time reversal invariance, and improves the precision of our previous best measurement6 by a factor of 4.3. The measurement tests the standard model at an energy scale of 1.96 × 10-27 gigaelectronvolts (confidence level 0.68), and improves ten coefficients of the standard model extension10. Our cyclotron clock study also constrains hypothetical interactions mediating violations of the clock weak equivalence principle (WEPcc) for antimatter to less than 1.8 × 10-7, and enables the first differential test of the WEPcc using antiprotons11. From this interpretation we constrain the differential WEPcc-violating coefficient to less than 0.030.

Sympathetic cooling of a trapped proton mediated by an LC circuit.

Efficient cooling of trapped charged particles is essential to many fundamental physics experiments1,2, to high-precision metrology3,4 and to quantum technology5,6. Until now, sympathetic cooling has required close-range Coulomb interactions7,8, but there has been a sustained desire to bring laser-cooling techniques to particles in macroscopically separated traps5,9,10, extending quantum control techniques to previously inaccessible particles such as highly charged ions, molecular ions and antimatter. Here we demonstrate sympathetic cooling of a single proton using laser-cooled Be+ ions in spatially separated Penning traps. The traps are connected by a superconducting LC circuit that enables energy exchange over a distance of 9 cm. We also demonstrate the cooling of a resonant mode of a macroscopic LC circuit with laser-cooled ions and sympathetic cooling of an individually trapped proton, reaching temperatures far below the environmental temperature. Notably, as this technique uses only image-current interactions, it can be easily applied to an experiment with antiprotons1, facilitating improved precision in matter-antimatter comparisons11 and dark matter searches12,13.

Direct limits on the interaction of antiprotons with axion-like dark matter.

Astrophysical observations indicate that there is roughly five times more dark matter in the Universe than ordinary baryonic matter1, and an even larger amount of the Universe's energy content is attributed to dark energy2. However, the microscopic properties of these dark components remain unknown. Moreover, even ordinary matter-which accounts for five per cent of the energy density of the Universe-has yet to be understood, given that the standard model of particle physics lacks any consistent explanation for the predominance of matter over antimatter3. Here we present a direct search for interactions of antimatter with dark matter and place direct constraints on the interaction of ultralight axion-like particles (dark-matter candidates) with antiprotons. If antiprotons have a stronger coupling to these particles than protons do, such a matter-antimatter asymmetric coupling could provide a link between dark matter and the baryon asymmetry in the Universe. We analyse spin-flip resonance data in the frequency domain acquired with a single antiproton in a Penning trap4 to search for spin-precession effects from ultralight axions, which have a characteristic frequency governed by the mass of the underlying particle. Our analysis constrains the axion-antiproton interaction parameter to values greater than 0.1 to 0.6 gigaelectronvolts in the mass range from 2 × 10-23 to 4 × 10-17 electronvolts, improving the sensitivity by up to five orders of magnitude compared with astrophysical antiproton bounds. In addition, we derive limits on six combinations of previously unconstrained Lorentz- and CPT-violating terms of the non-minimal standard model extension5.

A parts-per-billion measurement of the antiproton magnetic moment.

Precise comparisons of the fundamental properties of matter-antimatter conjugates provide sensitive tests of charge-parity-time (CPT) invariance, which is an important symmetry that rests on basic assumptions of the standard model of particle physics. Experiments on mesons, leptons and baryons have compared different properties of matter-antimatter conjugates with fractional uncertainties at the parts-per-billion level or better. One specific quantity, however, has so far only been known to a fractional uncertainty at the parts-per-million level: the magnetic moment of the antiproton, . The extraordinary difficulty in measuring with high precision is caused by its intrinsic smallness; for example, it is 660 times smaller than the magnetic moment of the positron. Here we report a high-precision measurement of in units of the nuclear magneton µN with a fractional precision of 1.5 parts per billion (68% confidence level). We use a two-particle spectroscopy method in an advanced cryogenic multi-Penning trap system. Our result = -2.7928473441(42)µN (where the number in parentheses represents the 68% confidence interval on the last digits of the value) improves the precision of the previous best measurement by a factor of approximately 350. The measured value is consistent with the proton magnetic moment, µp = 2.792847350(9)µN, and is in agreement with CPT invariance. Consequently, this measurement constrains the magnitude of certain CPT-violating effects to below 1.8 × 10-24 gigaelectronvolts, and a possible splitting of the proton-antiproton magnetic moments by CPT-odd dimension-five interactions to below 6 × 10-12 Bohr magnetons.

Measurement of Ultralow Heating Rates of a Single Antiproton in a Cryogenic Penning Trap.

We report on the first detailed study of motional heating in a cryogenic Penning trap using a single antiproton. Employing the continuous Stern-Gerlach effect we observe cyclotron quantum transition rates of 6(1) quanta/h and an electric-field noise spectral density below 7.5(3.4)×10^{-20} V^{2} m^{-2} Hz^{-1}, which corresponds to a scaled noise spectral density below 8.8(4.0)×10^{-12} V^{2} m^{-2}, results which are more than 2 orders of magnitude smaller than those reported by other ion-trap experiments.

BASE-STEP: A transportable antiproton reservoir for fundamental interaction studies.

Currently, the world's only source of low-energy antiprotons is the AD/ELENA facility located at CERN. To date, all precision measurements on single antiprotons have been conducted at this facility and provide stringent tests of fundamental interactions and their symmetries. However, magnetic field fluctuations from the facility operation limit the precision of upcoming measurements. To overcome this limitation, we have designed the transportable antiproton trap system BASE-STEP to relocate antiprotons to laboratories with a calm magnetic environment. We anticipate that the transportable antiproton trap will facilitate enhanced tests of charge, parity, and time-reversal invariance with antiprotons and provide new experimental possibilities of using transported antiprotons and other accelerator-produced exotic ions. We present here the technical design of the transportable trap system. This includes the transportable superconducting magnet, the cryogenic inlay consisting of the trap stack and detection systems, and the differential pumping section to suppress the residual gas flow into the cryogenic trap chamber.

Trap-integrated fluorescence detection with silicon photomultipliers for sympathetic laser cooling in a cryogenic Penning trap.

We present a fluorescence-detection system for laser-cooled 9Be+ ions based on silicon photomultipliers (SiPMs) operated at 4 K and integrated into our cryogenic 1.9 T multi-Penning-trap system. Our approach enables fluorescence detection in a hermetically sealed cryogenic Penning-trap chamber with limited optical access, where state-of-the-art detection using a telescope and photomultipliers at room temperature would be extremely difficult. We characterize the properties of the SiPM in a cryocooler at 4 K, where we measure a dark count rate below 1 s-1 and a detection efficiency of 2.5(3)%. We further discuss the design of our cryogenic fluorescence-detection trap and analyze the performance of our detection system by fluorescence spectroscopy of 9Be+ ion clouds during several runs of our sympathetic laser-cooling experiment.

A high-Q superconducting toroidal medium frequency detection system with a capacitively adjustable frequency range >180 kHz.

We describe a newly developed polytetrafluoroethylene/copper capacitor driven by a cryogenic piezoelectric slip-stick stage and demonstrate with the chosen layout cryogenic capacitance tuning of ≈60 pF at ≈10 pF background capacitance. Connected to a highly sensitive superconducting toroidal LC circuit, we demonstrate tuning of the resonant frequency between 345 and 685 kHz, at quality factors Q > 100 000. Connected to a cryogenic ultra low noise amplifier, a frequency tuning range between 520 and 710 kHz is reached, while quality factors Q > 86 000 are achieved. This new device can be used as a versatile image current detector in high-precision Penning-trap experiments or as an LC-circuit-based haloscope detector to search for the conversion of axion-like dark matter to radio-frequency photons. This new development increases the sensitive detection bandwidth of our axion haloscope by a factor of ≈1000.

Some genetic aspects of alcoholism and criminality. A population of adoptees.

The state criminal records and official registers of alcoholics were used in a study of 2,000 adoptees and their biological and adoptive parents. The frequency of registration for the adoptees were approximately the same as for the population in general, but for the biological parents it was two to three times greater. Very few adoptive parents appeared in the records. It is conceivable that to a large extent adoption neutralized the "social heritage" from the biological parents. There was, however, a significant correlation in the records between alcoholism in biological parents and in their adopted-out sons. On the other hand, the criminal records showed no such correlation between biological parents and their children. These results support the hypothesis that there is a genetic explanation for the development of alcoholism, but not for the manifestation of criminality.

Maternal inheritance of alcohol abuse. Cross-fostering analysis of adopted women.

The inheritance of alcohol abuse was studied in 913 Swedish women adopted by nonrelatives at an early age. There was a threefold excess of alcohol abusers among the adopted daughters of alcoholic biological mothers compared with other daughters. In addition, there was an excess of alcohol abuse among the daughters of biological fathers with alcohol abuse that was mild and not associated with criminality. However, fathers with extensive treatment for both alcoholism and criminality had no excess of alcoholic daughters. This confirms the heterogeneity among alcoholics noted in earlier work with adopted sons, which found that the latter type of criminal alcoholics also had no excess of alcoholic mothers. Imitation of alcohol abuse by adoptive parents did not increase later alcohol abuse by adopted women. The importance of nonfamilial environments and maternal effects is demonstrated for alcohol abuse in women.

Inheritance of alcohol abuse. Cross-fostering analysis of adopted men.

The inheritance of alcoholism was studied in 862 Swedish men adopted by nonrelatives at an early age. Both the congenital and postnatal backgrounds of the adoptees modify their risk for alcohol abuse. We distinguish two forms of alcoholism that have distinct genetic and environmental causes and differ in their association with criminality, severity of alcohol abuse, and the frequency of expression in biological mothers. Postnatal milieu determines the frequency and severity of expression of the common type of susceptibility in both men and women. In contrast, the less common type is highly heritable in men but is seldom expressed in mothers of affected men.

Replication of the Stockholm Adoption Study of alcoholism. Confirmatory cross-fostering analysis.

BACKGROUND: Two forms of alcoholism with distinct clinical features and mode of inheritance were first distinguished in the Stockholm Adoption Study. This involved a large sample of children born in Stockholm, Sweden, who were adopted at an early age and reared by nonrelatives. Type 1 alcoholism had adult onset and rapid progression of dependence without criminality, whereas type 2 had teenage onset of recurrent social and legal problems from alcohol abuse. METHODS: A replication study was carried out with 577 men and 660 women born in Gothenburg, Sweden, and adopted at an early age/by nonrelatives. The genetic and environmental backgrounds of the adoptees were classified by the exact procedures calibrated by discriminant analysis in the original study. RESULTS: Both type 2 and severe type 1 alcoholism were confirmed as independently heritable forms of alcoholism in male adoptees. The lifetime risk of severe alcoholism was increased 4-fold in adopted men with both genetic and environmental risk factors characteristic of type 1 alcoholism compared with the others (11.4% vs 3.0%). Neither genetic nor environmental risk factors for type 1 alcoholism by themselves were sufficient to cause alcoholism. In contrast, the risk of type 2 alcoholism was increased 6-fold in adopted sons with a type 2 genetic background compared with others; regardless of their postnatal environment (10.7% vs 2.0%). The sons with a type 2 genetic background in the replication sample had no excess of type 1 alcoholism, and vice versa. There was no increased risk of mild abuse in adopted men regardless of their genetic or environmental background. CONCLUSION: Type 1 and type 2 alcoholism are clinically distinct forms of alcoholism with causes that are independent but not mutually exclusive.

An adoption study of somatoform disorders. I. The relationship of somatization to psychiatric disability.

The relationship between psychiatric impairment and disability due to somatic complaints was studied in 859 women adopted at an early age by nonrelatives in Sweden. The clinical data were derived from the comprehensive registrations for all medical treatment and sick-leave compensation that are kept about Swedish residents by the National Health Insurance Board. The adoptees were compared with nonadopted controls who were individually matched for social and demographic variables. We identified a somatization syndrome that is consistently associated with psychiatric impairment and repeated brief periods of disability with chief complaints of headache, backache, and abdominal distress on different occasions. A method for clinically distinguishing "somatizers" from other women was derived in one sample and was shown to have a classification accuracy of 97% in a replication sample. Somatizers accounted for 36% of all cases of psychiatric disability and 48% of all sick-leave occasions in adopted women. Compared with nonadoptees, there was an excess of somatizers in adoptees, a population known to have an excess of biological parents who are criminal and/or alcoholic.

An adoption study of somatoform disorders. II. Identification of two discrete somatoform disorders.

linical heterogeneity among women with prominent somatization was studied in a population of 859 adopted women in Sweden. We distinguished two groups of "somatizers" who differ in both the diversity of their somatic complaints and the frequency of their periods of disability. Type 1 or high-frequency somatizers have a high frequency of psychiatric, abdominal, and back complaints. Type 2 or diversiform somatizers have less frequent disability, but a greater diversity of complaints per occasion than do other somatizers. Diversiform somatizers have psychiatric chief complaints or backache in a lower proportion of their sick periods than either high-frequency somatizers or nonsomatizers. Quantitative measures of frequency and diversity were derived in a series of discriminant analyses. The distribution of scores on these measures indicated that high-frequency somatization and diversiform somatization were discrete disorders with little clinical overlap and rare intermediate cases. This demonstration of two discrete types of somatizers was confirmed in a replication sample.

An adoption study of somatoform disorders. III. Cross-fostering analysis and genetic relationship to alcoholism and criminality.

The genetic and environmental antecedents of two clinically distinct somatoform disorders were compared in 859 Swedish women adopted at an early age by nonrelatives. The characteristics of both the biological and adoptive parents of high-frequency "somatizers" were different from those of diversiform somatizers. The risk of diversiform somatization was increased in the adopted-away daughters of men treated for male-limited (type 2) alcoholism, but not in daughters of milieu-limited (type 1) alcoholics. In contrast, the biological fathers of high-frequency somatizers often had a history of recurrent convictions for violent crimes since adolescence, but no treatment for alcoholism. Similarly, alcohol abuse by the adoptive father was associated with increased risk of diversiform but not high-frequency somatization. Thus, high-frequency and diversiform somatization are not only clinically distinct, but also have different genetic and environmental backgrounds. The association of diversiform somatization with male-limited alcoholism, and not with milieu-limited alcoholism, also provides independent support for our earlier distinction between these two types of alcoholism.

Predisposition to petty criminality in Swedish adoptees. I. Genetic and environmental heterogeneity.

The inheritance of criminality was studied in 862 Swedish men and adopted by nonrelatives at an early age. If type of offense and association with alcohol abuse were neglected, criminality was heterogeneous and appeared to be largely nonfamilial. Nevertheless, different genetic and environmental antecedents influenced the development of criminality, depending on whether or not there was associated alcohol abuse. Alcoholic criminals often committed repetitive violent offenses, whereas nonalcoholic criminals were characterized by commission of a small number of petty property offenses. These nonalcoholic petty criminals had an excess of biologic parents with histories of petty crime but not alcohol abuse. In contrast, the risk of criminality in alcohol abusers was correlated with the severity of their own alcohol abuse, but not with criminality in the biologic or adoptive parents. Unstable preadoptive placement was associated with increased risk for petty criminality, whereas low social status was associated with alcohol-related criminality. We discuss the significance of these results in relation to the classification of criminals and current concepts about antisocial personality.

Predisposition to petty criminality in Swedish adoptees. II. Cross-fostering analysis of gene-environment interaction.

The interaction of congenital and postnatal antecedents of criminality was studied in 862 Swedish men adopted at an early age by nonrelatives. Most explained variability was due to differences between the genetic predispositions of the adoptees, but substantial contributions were also made by postnatal environment, either alone or in combination with specific genetic subtypes. There was no overlap between the congenital antecedents of alcoholism and nonalcoholic criminality, but some postnatal variables were common to criminality and one type of alcoholism that is limited to expression in men, according to earlier studies. Low social status alone was not sufficient to lead to criminality, but did increase risk in combination with specific types of genetic predisposition. Unstable preadoptive placements contributed to the risks of both petty criminality and male-limited alcoholism, but not to other types of alcohol abuse. We discuss these results in terms of their clinical and social implications.

Predisposition to petty criminality in Swedish adoptees. III. Sex differences and validation of the male typology.

Sex differences in the inheritance of criminality were studied in 913 women and 862 men from the Stockholm Adoption Study. Our multivariate classification of genetic heterogeneity was validated in the female sample by confirmation of predictions derived from the men. The congenital antecedents of criminality were the same regardless of sex, but the congenital predisposition to criminality had to be more severe for a woman to be affected. Furthermore, the postnatal antecedents of criminality that were studied were qualitatively different in the two sexes. Prolonged institutional care and urban rearing increased the risk of criminality in women but not in men. In contrast, multiple temporary placements and low social status of the adoptive home increased the risk ot criminality in men but not women. The antecedents of petty criminality and alcohol abuse were distinct in both sexes. Cross-fostering analysis indicated that postnatal factors were more important for criminality than for alcoholism in women. We discuss the overall significance of this series of reports and make suggestions for future research.

An adoption study of depressive disorders and substance abuse.

Registered psychiatric illness was studied in the biologic and adoptive parents of 115 adoptees with affective disorders or histories of substance abuse. The parents of these patients were compared with those of 115 control subjects who were pairwise matched for demographic and social variables and who had no psychiatric illness. Psychiatric patients had a fivefold excess of adoptive fathers who had psychiatric illness compared with fathers of their matched controls. This was due to an excess of affective disorders in adoptive fathers regardless of the sex or diagnosis of the adopted child. Biologic mothers of female patients had a threefold increase in psychiatric illness compared with mothers of their matched controls and a fourfold increase compared with mothers of male adoptees. However there was no significant concordance between specific diagnoses in biologic parents and their adopted-away children. Subdivision of depressive patients according to psychotic-nonpsychotic and reactive-nonreactive dichotomies did not yield subgroups with distinct family histories.

The genetics of alcoholisms and related disorders.

The inheritance of alcohol abuse and other psychopathology in 862 men and 913 women adopted by non-relatives, was studied. Both male and female adoptees were at greater risk to develop alcohol abuse if their biological, but not their adoptive, parents were alcoholic. Three types of families with alcoholism were distinguished that differed in frequency of alcohol abuse, somatoform disorders in women and in relation to antisocial behaviour in male adoptees. The combination of both genetic and environmental risk factors was necessary for the development of alcoholism in the most common, milieu-limited type of alcoholism. In families with a less common, male-limited, type of vulnerability, alcohol abuse was highly heritable in men, but women had multiple somatic complaints and seldom abuse. In a third type of family the common vulnerability was expressed as antisocial behavior with violent criminality and recurrent alcohol abuse in males, but as high frequency somatization in female relatives.