Particle physicists’ long-held hopes of discovering exotic new particles have been dashed after a measurement of the humble electron. The finding, which was published in Science today, demonstrates with greater precision than ever before that the electron’s electric charge distribution is essentially circular. The outcome suggests that any new central particles prowling unseen in the vacuum may be excessively monstrous for even the world’s greatest molecule smasher, the Huge Hadron Collider (LHC), to deliver.
John Doyle, a physicist at Harvard University and co-leader of a competing experiment that established the previous limit on a charge asymmetry known as the electric dipole moment, states, “It’s a fantastic result.” Because the methods are so different, it is clear that we both came up with the same result—theirs is better by a factor of two.” According to Doyle, the result may also make it more difficult for theorists to explain how the early universe produced more matter than antimatter.
Physics proposes that some of the rules governing the interactions of fundamental particles must look different if run forward or backward in time, implying that matter and antimatter behave slightly differently, in order to explain how that imbalance developed and, consequently, why anything exists at all. In point of fact, the interactions between quarks, which are the building blocks of protons and neutrons, do break this symmetry, but not enough to cause the imbalance between matter and antimatter in the universe.
In this way, physicists think some at this point unseen particles, past the recognizable ones in their predominant standard model, compensate for any shortfall. Due to quantum uncertainty, which holds that all particles, even those too heavy to be produced with an atom smasher, flit in and out of the vacuum surrounding it, those particles could influence the electron even though they are invisible. On the off chance that that cloudiness contains particles whose cooperations disregard the time-inversion balance, they ought to present properties that abuse that evenness on the electron also.
This kind of property would be the electric dipole moment. If the electron’s negative charge is symmetrical, then simply reversing its spin and the direction of its magnetism would result in its appearance reverting to that of the initial electron. However, time-reversal symmetry would be broken if the electron had an electric dipole moment in which, for instance, more negative charge was moved toward its south pole and less positive charge was moved toward its north pole. Its magnetism, but not its static charge distribution, would be altered by reversing time, resulting in a particle distinct from the original electron.
With so much at stake, some physicists have searched for decades for the electric dipole moment of the electron. According to Eric Cornell, a physicist at the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder (CU Boulder) who is a co-author of the new study, doing that is straightforward in principle.
Let’s say you put an electron in a vertical magnetic field with its magnetism pointing horizontally. The field will make the electron whirl opposite to the field. An electric field pointing in the same direction as the magnetic field will accelerate the electron’s twirl if the electron also has an electric dipole moment. The electron will twirl slightly slower if the electric field is flipped in the opposite direction. According to Cornell, the experiment consists of applying such fields and observing this minute shift in the frequency of the electron’s twirling.
Finding a sufficiently strong electric field is the tricky part. Cornell; Jun Ye, a CU Boulder and NIST physicist; and coworkers used the extreme conditions inside an ionized hafnium fluoride molecule. An electron experiences a 20 billion volts per centimeter electric field in the bond between hafnium and fluorine atoms. To put it more succinctly, the physicists used an electric field from the outside to shift the powerful internal field of the molecular ion in relation to a magnetic field. They also watched for changes in the frequency at which the electrons inside twirled.
In practice, layers of technology were needed to trap the ions, send the electrons inside them twirling, and, after a variable amount of time, blow up the molecules with a laser to find which way the electrons were pointing. Key was the capacity to hold the particles for as long as 2 seconds in an exceptional snare, empowering the electrons inside the atoms to spin many times, says Tanya Roussy, lead writer on the paper, who as an alumni understudy at CU Rock dealt with the trial for quite some time. Although many ion traps can fit on microchips, Roussy claims that “our trap is huge.” It could hold a Starbucks cup.
In the end, the team was unable to locate any evidence that the electron possesses an electric dipole moment. The measurement resulted in a decrease of the moment’s strength limit by 2.4. Because lighter particles would have a greater impact, that limit implies a lower limit on the mass of any unobserved particles that would violate time-reversal invariance. That cutoff is around 3 or 4 teraelectron volts, Cornell says, about a component of 2 heavier than the LHC can create.
The new mass cutoff doesn’t completely preclude revelations at the LHC, alerts Nicholas Hutzler, a physicist at the California Organization of Innovation. New particles that don’t disregard the time balance might in any case exist in the LHC’s grip. ” According to Hutzler, these tabletop experiments are the most sensitive for some things, but not for others.
Curiously, Roussy states that she is not entirely disappointed that the team’s null result did not conflict with the standard model, which appeared to be insurmountable. She says, “You’re kind of hoping in secret for not zero because that would be the big discovery.” But what if the result is incorrect if it is not zero? You’re also hoping for zero because it’s so scary.