Release Date: March 1, 1998
BUFFALO, N.Y. -- Fourteen years ago, conflicting reports of unusual subatomic particles called anomalons generated a controversy among particle physicists so divisive that it practically squelched all investigation into the subject.
Now Piyare Jain, Ph.D., UB professor of physics, is having the last word.
His results, published today (March 1, 1998) in the British Journal of Nuclear and Particle Physics, provide the first indisputable evidence that anomalons -- which contradict conventional laws of physics -- do exist, but only for a billionth of a second under very specific conditions during nuclear interactions.
With this paper, Jain anticipates revitalizing inquiry into a phenomenon that many physicists abandoned, opening a world of possibilities for other experimentalists in search of new forms of matter.
The results suggest that new and exotic states of matter, such as the H particle, predicted by the quantum chromodynamic theory 20 years ago but never found, may finally be detectable.
"We have proven the existence of these very abnormal nuclear interactions called anomalons," said Jain. "It is possible that they could be implicated in all the mysteries we have not yet solved, such as the quark-gluon plasma, black holes and detection of new, exotic particles."
Detection of the H particle would be an extraordinary finding, since the quantum chromodynamic theory predicts that it is composed not of two or three quarks, as is all matter that is currently known, but rather of six quarks.
In recent publications, three different experimental groups have reported no success in their search for the H particle.
Jain's success in detecting the anomalon holds out promise that the H particle -- and other exotic states of matter predicted by this theory, but never found -- also may be detectable.
The research resolves fundamental questions about anomalons raised in the 1980s by groups from the University of California at Berkeley and elsewhere, some of whom claimed to have detected the particles under a variety of conditions and others who claimed not to have detected them at all.
"Finally, I have vindication," said Jain. "In 1984, my colleagues thought this was a dead issue. With this paper, I am saying that there is a pulse and the heart is beating; they were just using the wrong stethoscope to look for it."
His results are all the more noteworthy since he has done it with the assistance of only one postdoctoral researcher, at a time when particle physicists routinely work in groups of 40 or 50 or more.
Anomalons are the highly reactive, extremely short-lived particles that sometimes are created in the violent collisions between incoming, heavy projectile particles and target nuclei in accelerator experiments.
The particles are considered abnormal or "anomalous" because they are far more reactive and they decay far more quickly than such fragments are expected to, according to the theory of strong interactions.
In the 1980s, several groups claimed that they had observed intensely reactive, anomalous particles during some accelerator experiments.
While some noted that they could not find evidence for anomalons when the fragments of certain masses of the incoming beam were accelerated to a certain nuclear energy, others reported that they could.
In 1984, at an international conference on heavy ions, Jain took issue with his colleagues at Berkeley. They questioned the existence of anomalons based on the fact that they could not find evidence of them when lighter fragments, rather than the heavier fragments of heavy-ion beams, were used.
Jain published his initial results from experiments with iron and argon beams in two, independent papers published in 1982 and 1984 in Physical Review Letters. Those papers showed that a small percentage of fragments generated after nuclear collisions, which were heavier than those used by the Berkeley experiments, did not behave according to conventional theories of strong interactions.
"At the time, I said I disagreed with my colleagues and that only time would tell," recalled Jain. "I knew that with a heavy-ion beam with energy higher than 2 billion electron volts per nucleon and mass higher than 20 nucleon masses, I could prove what I knew, but I was helpless: There was no high-energy, heavy-ion beam available in 1984."
Jain's recent experiments were conducted at Brookhaven National Laboratory (BNL) with a gold beam. The beam accelerates gold nuclei to 10 billion electron volts per nucleon, producing a total of about 2 trillion electron volts of energy per interaction collision. Gold at BNL and lead at CERN in Switzerland are the highest-energy beams available to physicists today.
"The theory of strong interactions tells you so many interactions should take place," said Jain. "In our experiments, we found 51 percent more interactions than that theory predicts."
According to Jain, the extremely rapid decay (approximately 1 billionth of a second) of the anomalons, which cannot be missed by his special detector, is the reason behind the increased number of observed interactions.
The new particles are produced during the initial impact, when the incoming-beam nuclei collide with the target nuclei.
For that flash of an instant, the anomalons hitch a ride on the nuclear fragments, travel briefly with them for a few hundred microns and then decay.
According to Jain, that short distance, (one millimeter equals 1,000 microns) signifies the particle's brief lifetime and is critical.
Because of their rapid decay, the interactions can be easily missed if the proper detector is not used, Jain explained.
"These events would have been missed if the target had a thickness greater than this travel distance," said Jain.
In fact, said Jain, that was the problem with the previous experiments at other institutions, which used electronic detectors whose targets are several centimeters thick, compared to a few microns thick.
"The lifetimes of such particles are too short to be seen by electronic detection," said Jain. "The reaction dies in the target, and so it cannot be observed."
Jain describes his detection method as "a poor man's technique."
It stands in marked contrast to the multi-million-dollar electronic detectors -- in some cases as large as one-story buildings -- that are the technique-of-choice among many of the large-particle-physics research groups working today.
Jain has developed his own special, photosensitive detectors made from ordinary photographic film mounted on glass.
The photographic emulsion has the highest-possible space resolution, i.e. the extremely small angles at which the particles are produced in these high-energy nuclear collisions.
With this method, where the emulsion acts as target and detector at the same time, the produced particles in nuclear collisions can be traced for their speed, distance, the time it takes to travel and the direction in which they travel.
The detectors, small enough to hold in one hand, register results that allow the scientists, using a customized microscope, to see the interactions between individual particles.
It is a painstaking approach in which Jain personally examines the "tracks" made by nuclear collisions in the photosensitive detectors.
According to Jain, the fact that a particle with such a short lifetime can be detected is especially tantalizing because it provides scientists with the first real piece of evidence that other exotic, heavy particles with similarly short lifetimes, such as the H particle, at last may be detected.
"We have proven that this abnormal behavior during nuclear interactions is there, and that there is a large number of these interactions," said Jain. "One of them just might be producing the H particle."