MSGID: 1:317/3 63db3c6b   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Amplified search for new forces    
    Special setup uses polarized rubidium and xenon as transmitter and   
   receiver system for exotic fields    
      
     Date:   
         February 1, 2023   
     Source:   
         Johannes Gutenberg Universitaet Mainz   
     Summary:   
         In the search for new forces and interactions beyond the Standard   
         Model, an international team of researchers has now taken a good   
         step forward.   
      
         The researchers are using an amplification technique based   
         on nuclear magnetic resonance. They use their experimental   
         setup to study a particular exotic interaction between spins:   
         a parity-violating interaction mediated by a new hypothetical   
         exchange particle, called a Z' boson, which exists in addition to   
         the Z boson mediating the weak interaction in the standard Model.   
      
      
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   FULL STORY   
   ==========================================================================   
   In the search for new forces and interactions beyond the Standard Model,   
   an international team of researchers involving the PRISMA+ Cluster of   
   Excellence at Johannes Gutenberg University Mainz (JGU) and the Helmholtz   
   Institute Mainz has now taken a good step forward. The researchers, among   
   them Prof. Dr. Dmitry Budker, are using an amplification technique based   
   on nuclear magnetic resonance. In their work recently published in Science   
   Advances, they use their experimental setup to study a particular exotic   
   interaction between spins: a parity-violating interaction mediated by a   
   new hypothetical exchange particle, called a Z' boson, which exists in   
   addition to the Z boson mediating the weak interaction in the standard   
   Model. In the current setup, they were unable to detect this particle,   
   but they were able to increase the sensitivity by five orders of magnitude   
   compared to previous measurements. This allows to set constraints on the   
   strength of the interaction of the new exchange particle with Standard   
   Model particles that are complementary to astrophysical observations   
   and open up a previously inaccessible region.   
      
      
   ==========================================================================   
   Numerous theories predict the existence of exotic interactions beyond   
   the Standard Model. They differ from the four known interactions and   
   are mediated by previously unknown exchange particles. In particular,   
   parity-violating interactions, i.e., where mirror-symmetric is broken,   
   are currently experiencing a special interest. On the one hand, because   
   this would immediately indicate the particular type of new physics we are   
   dealing with, and on the other hand, because their effects are easier   
   to separate from spurious systematic effects, that usually do not show   
   mirror-symmetry breaking.   
      
   "In the current article, we take a close look at such an interaction   
   between the spins of electrons and the spins of neutrons, mediated by a   
   hypothetical Z' boson. In a mirrored world, this interaction would lead   
   to a different result; parity is violated here," explains Dmitry Budker.   
      
   This "result" looks like this: The electron spins within a source are   
   all aligned in one direction, i.e. polarized, and the polarization is   
   continuously modulated, thus creating an exotic field that is perceived   
   as a magnetic field and can be measured using a sensor. In a mirrored   
   world, the exotic field would not point in the same direction as would   
   be expected in a "real" mirror image, but in the opposite direction:   
   the parity of this interaction is violated.   
      
   SAPPHIRE -- the new gem in the search for new physics "Spin Amplifier   
   for Particle PHysIcs REsearch" -- SAPPHIRE for short -- is what the   
   researchers have named their setup, which is based on the two elements   
   rubidium and xenon. They have already used this technique in a similar   
   form to search for other exotic interactions and for dark matter fields.   
      
   Specifically, in the experimental search for exotic spin-spin   
   interactions, two chambers filled with the vapor of one of the two   
   elements are positioned in close proximity to each other: "In our   
   experiment, we use polarized electron spins of rubidium-87 atoms as a   
   spin source and polarized neutron spins of the noble gas xenon, or more   
   precisely the isotope xenon-129, as a spin sensor," says Dmitry Budker.   
      
   The trick is that the special structure and the polarized xenon atoms   
   in the spin sensor initially amplify the field generated in the rubidium   
   source: thus, the effect triggered by a potential exotic field would be   
   a factor of 200 larger. Now the principle of nuclear magnetic resonance   
   comes into play, i.e.   
      
   the fact that nuclear spins react to magnetic fields that oscillate at   
   a certain resonance frequency. Rubidium-87 atoms are also present in a   
   small proportion in the sensor cell for this purpose. They in turn act   
   as an extremely sensitive magnetometer to determine the strength of the   
   resonance signal.   
      
   The detection of such an exotic field in the right frequency range would   
   then be the clue to the new interaction we are looking for. Other special   
   experimental details ensure that the setup is particularly sensitive in   
   the frequency range of interest and less sensitive to spurious effects   
   from other magnetic fields that inevitably also arise in the experiment.   
      
   "All in all, this is a rather intricate setup that has required a   
   careful design and calibration. It is highly rewarding to work on such   
   challenging and interesting problems with our long-time collaborators   
   from the University of Science and Technology (USTC) in Hefei, China   
   who hosted the experiment," reports Dmitry Budker.   
      
   After successful proof-of-principle, the scientists started the first   
   series of measurements to search for the exotic interaction. Although   
   they have not yet been able to find a corresponding signal after 24 hours   
   of measurements, the five orders of magnitude increase in sensitivity   
   has enabled them to set constraints on the strength of the new exchange   
   particle's interaction with Standard Model particles. Further optimization   
   could even improve the experimental sensitivity to the special exotic   
   interaction by another eight orders of magnitude. This makes it seem   
   possible to use the ultrasensitive SAPPHIRE setup to discover and study   
   a new physics with potential Z' bosons.   
      
       * RELATED_TOPICS   
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   ==========================================================================   
   Story Source: Materials provided by   
   Johannes_Gutenberg_Universitaet_Mainz. Note: Content may be edited for   
   style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Yuanhong Wang, Ying Huang, Chang Guo, Min Jiang, Xiang Kang,   
      Haowen Su,   
         Yushu Qin, Wei Ji, Dongdong Hu, Xinhua Peng, Dmitry Budker. Search   
         for exotic parity-violation interactions with quantum spin   
         amplifiers.   
      
         Science Advances, 2023; 9 (1) DOI: 10.1126/sciadv.ade0353   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/02/230201134227.htm   
      
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