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Declassified in Part - Sanitized Copy Approved for Release 2014/01/09: CIA-RDP79-00999A000200010093-3 LI CORVIDENTIAL U SECRET 1_11? UNCLANNI USE ONLY ROUTING AND RECORD SHEET SUBJECT: (Optional) FROM: .414 PtAt , EXTENSION NO. STAT STAT 4TE TO: (Officer designation, room number, and building) DATE OFFICER'S INITIALS COMMENTS (Number each comment to show from whom to whom. Draw a line across column after each comment.) RECEIVED FORWARDED A.164, gess 2. 2cc Steerl& 7314. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. FORM 61 0 3-62 USEDMEOVaUS r-7 SECRET El CONFIDENTIAL 1-1INTERNAL n IIMtI accirirn Declassified in Part - Sanitized Copy Approved for Release 2014/01/09: "o1A--ii5P79-00999A000200010093-3 e_ C . Declassified in Part - Sanitized Copy Approved for Release 2014/01/09: UIA-RDH79-00999A000200010093-3 Michael IN? E.reisier I 11C1.-t; r elb -111W1-1_4161.11 Particles? During the last few years there has been an effort to search for tachyons? particles that travel faster than the speed of light. I hope to show here that there is, in fact, some justifica- tion for a search for particles that would seem to violate all we have learned about special relativity?and for the very modest investment that has been devoted to the question. The experiments that have been performed to look for these particles will be reviewed, and I will avoid, for the most part, any lengthy dis- cussion of the wealth of recent the- oretical papers in which the debate about the existence of these particles still rages. It has become almost traditional in this subspecialty to begin with a well- known limerick: A certain young lady named Bright Could travel much faster than light. She departed one day In a relative-way And returned on the previous night. Now that we have observed tradi- tion, we turn to a more serious con- sideration of these weird particles. As is well known, the expression for the energy E of a normal particle of rest mass mo which is traveling ; with a velocity v is given by Michael N. Kreisler is an Associate Professor of physics at the University of Massachusetts at Am- herst. He received his Ph.D. in high-energy physics ; particle research from Stanford University in 1966 and taught physics at Princeton Uni- versity before joining the faculty at the University tf Massachusetts. flis research has concentrated on :leasuren,erts of. hz1g1:--c7er.g), neut,n rnierartions ; studies of multipion resonances, and searches for rare decays of elementary particles. This work has been supported in part by the National Science ; Foundation. Address: Department of Physics and Astronomy, University of Massachusetts, Am- ?e view of the hAbotheses about the nature of tachyons and of -experimental searches for them E ? moci ? (v/c)2 where c is the speed of light. This expression indicates that accelerating a particle to speeds equal to or greater than the speed of light requires an infinite amount of energy and there- fore should be impossible. It is this fact that led Einstein to state that "velocities greater than that of light have no possibility of existence" (7). In addition, this fact and the appar- ent problems that faster-than-light particles would create in special rel- ativity--in particular causal para- doxes?have been strong enough the- oretical arguments to deter any in- vestigations in the area. We shall return to these paradoxes below. Although theorists, including Som- rnerfeld (2), had considered such particles as early as 1904 (in pre- special relativity days), it was not until the work of Bilaniuk, Deshpande, and Sudarshan in 1962 and then Feinberg in 1967 that the subject became of interest again. Bilaniuk, Deshpande, and Sudarshan (3) count- ered the first objection regarding infinite energy input by noting that we are all quite happy with the exis- tence and creation of photons and neutrinos, both of which always travel at the speed of light. Their proposal was to postulate the existence or crea- tion of particles with velocities always greater than c, thereby circumventing the infinite energy requirement. The possibility of these new particles is rather appealing because their existence would indicate an inter- esting syininetiy?narnely,_ there would be three allowed types of par- ticles, classified by their velocities: 1. Normal particles, which travel 2. Particles such as photons and massless particles which only exist if jai = c always 3. Particles with vl > c always Feinberg (4) introduced the name tachyons, from the Greek word mean- ing swift, for the third type of particles. This name has become quite fashion- able, and, as an interesting aside, its quick acceptance has led to other proposals for new names for normal particles?bradyons, from the Greek for slow, and tardyons, a name with an obvious derivation. While per- haps amusing, these names are not very useful and we will avoid them. Countering the objections of causal paradoxes is not as simple as merely postulating new particles. In order to discuss the problem, we must first examine the paradoxes implied by the existence of tachyons. In standard fashion, as shown in Figure 1, we consider two coordinate frames S and S' which have a common x axis. The frame S' moves at a constant velocity a (jai < c) in the +x direc- tion relative to S. Now, let us assume that an observer in S sees a tachyon created at point A at time tA. The tachyon travels with a velocity -Fu to point B where it is absorbed at time tB. For this observer, the dis- tance and time separations were both positive: At = tB ? tA > 0 Ax = xB ?XA > 0 Using the standard Lorentz trans- formation, we can calculate what an observer in the S, or moving, frame sees: Ax' = y(Ax ? vat) = (Ar vAx (1 ? Declassified in Part - Sanitized Copy Approved for Release 2014/01/09: CIA-RDP79-00999A000200010093-3 Declassified in Part - Sanitized Copy Approved for Release 2014/01/09: CIA-RDP79-00999A000200010093-3 At \ithe particular event. Carrying these = 7 (At ? 14, At?u) = 7t(1 ? c- v2) - where 7 = (1 ? c 2 In)C2 Clearly, the spatial separation Ax or Ax' is positive in both frames. How- ever, if the velocity of the tachyon is chosen such that uv > c2, separation for the moving is negative! Apparently a exists, because the observer tachyon absorbed before created! the time observer paradox sees the it was The paradox can be resolved by using the "reinterpretation principle," which is merely the statement that, when going from one inertial frame to another, it is essential that the form of physical laws be invariant. How- ever, there is no requirement that the description or interpretation of a particular phenomenon be the same. So long as there is no violation of a physical law in either frame, ob- servers in different frames could inter- pret a given series of events differently. In the case described above, the physical process was the passage of a tachyon between points A and B. The paradox is resolved if the observer in the S' -frame interprets the process as the creation of the tachyon at B and absorption at A. The observers then agree on the physical process but disagree about the interpretation of arguments further, if the tachyons are charged or carry any other quan- tum numbers, the observer in S' must see an anti-tachyon traveling from B to A (see Fig. 1). Before considering a more difficult paradox, there are certain character- istics of tachyons that must be men- tioned. The calculations that were -sketched above indicate that the sign of the fourth component of a tachyon four-vector can be changed by a Lorentz transformation. In other words, those tachyons that are travel- ing backward in time in a given frame also appear to have negative energies. Another interesting possibility that exists if there are tachyons is the de- cay of a normal, moving particle into itself plus a tachyon. Such de- cays without tachyons are forbidden, owing to the requirements of simul- taneous energy and momentum conservation. We will use these prop- erties of tachyons in the discussion of the following paradox. Consider our two observers again, one moving at a velocity v with re- spect to the other (see Fig. 2). These two observers, A and B, agree on the following course of action: A, the stationary observer, will send a tachyon to 'B at 12:00 noon his (A's) time unless he has received a tachyon from B before noon. B, upon receiving the tachyon from A, will immediately send a tachyon back to A. In the happy event that their relative velocity ah4the velocity of the tachyons are such that the Lorentz transformation between the frames does not reverse the sign of t or E, everything is fine. That is, A sends his tachyon out at noon and gets a return signal some- time later. However, if we are not so lucky, the tachyon emitted by B will be trayeling backward in time as viewed from the stationary frame. It will therefore arrive at A before noon. A will detect it and not send out his tachyon. Why then did B send one. back? This paradox may be resolved (4) if we examine A's detector, which, for this purpose, can be an atom or a proton. When the detector absorbs a positive-energy tachyon, its energy increases and either the proton moves or the atom goes into an excited state. If the observer wants to be sensitive only to positive-energy tachyons, his detector must consist of stationary protons or atoms in the ground state. Such detectors are not able to absorb negative-energy tachyons, and the paradox would not arise. If he wants to be sensitive to both positive and negative energies, he must choose, for example, a proton with some nonzero kinetic energy. The signal that a negative-energy tachyon had been absorbed would be a sudden loss of energy by the proton (for ex- ample, it could suddenly come to rest). However, the observer would in principle be unable to distinguish that absorption of a negative-energy tachyon from the spontaneous emis- sion of a positive-energy one. For that reason, he would assume that at 11:00 his detector spontaneously emitted a tachyon and would not attribute it to a signal from B. There- fore, the paradox is explained. The resolution of such simple ex- amples does not mean that appar- ently unresolvable paradoxes cannot be invented. In fact, arguments re- garding the existence of tachyons have filled many journal pages in recent months. However, as there was no compelling argument against their existence and since a good ex- perimental result is usually worth more than a journal of theoretical speculations, Torsten Alvager and I (5) decided to see if the question of tachyons was amenable to experi- Figure 1. An example of a possible paradox. sorbed at B. In frame S' (right/ the movie?. Ment If we were fortunate enough r Declassified in Part - Sanitized Copy Approved for Release 2014/01/09: CIA-RDP79-00999A000200010093-3 1. Declassified in Part - Sanitized Copy Approved for Release 2014/01/09 : CIA-RDP79-00999A000200010093-3 LLUYV UU tatAfruits uctrave: 'Ames? " Before an experimental search could be conducted, it. was first necessary to determine the properties that tachyons 'should exhibit. In what ways do they differ from normal par- ticles? Do present experimental re- sults put stringent limits on their existence? We present a partial list of the properties of tachyons. 1. The relativistic expressions for the energy and momentum of a par- ticle of rest mass m and traveling at velocity u are E ? 11 ? (u / c) 2 / "11111 IP' MC2 {1 ? (u/c)2}V' If jul is greater than c, the "rest mass," m, must be an imaginary quantity if the observable quantities E and lp I are to remain real. Since a tachyon rest mass is unobservable, this choice is allowed. We will use the notation m = jj.i, where 12 is a real number. Thus for tachyons: The relation between energy and momentum is then E2. = p12c2_ .z2c4 instead of the same expression Nith a plus sign, which holds for lormal particles. If the discussion s restricted to positive-energy :achyons, the bounds on the energy tnd momentum are 0 < E < co and p.c. < jp! < co These relations indicate several re- narkable properties of tachyons: (1) achyons can exist with zero total :nergy and with finite momentum; 2) infinite velocities are possible; md (3) when a tachyon loses energy, t accelerates !. A tachyon appears to be a tachyon n all Lorentz frames. In Figure 3 he algebra of velocity addition is iresentecl. If the velocity is greater han c in one frame, the Lorentz ransformation to any other frame eaves the velocity greater than c. A will sendB a tachyon at 12:00 his (A's) time unless B sends him a tachyon signal before noon. B will only send A a tachyon after he receives One from A. A's clock I haven't received a signal from B. I'll send him a tachyon. .1? Ah ha! Here's A's tachyon. I'll send him back one. The tachyon travels backward in time as viewed from A's coordinate frame. Here's B's signal. I won't send him a tachyon at noon. < Why did B send A a tachyon? total energy, they can in principle be created with zero energy input. One is then led to expect spontaneous tachyon production independent of the value of Ai. However, Feinberg (4), who has shown that it is possible to include tachyons in the formalism of relativistic quantum mechanics, claims that tachyons most probably obey Fermi-Dirac statistics. In that event, spontaneous production would be severely limited because all the energy states possible to reach via spontaneous creation would be filled, inasmuch as the exclusion principle allows at most a single particle obey- ing Fermi-Dirac statistics in each avail- able freely specified quantum state. 4. It is kinematically allowed for a tachyon to decay into itself plus a photon. This type of decay is not permitted for normal particles since taneously. For charged tachyons, it is in fact possible to calculate both the energy spectrum of the photons emitted and a total decay rate. This process yields many of the same fea- tures as Cerenkov emission, which for normal particles occurs when the velocity of particle propagation in a medium exceeds the velocity of light in that medium. For tachyons, of course, the velocity is always greater than the speed of light?even in a vacuum. Due to the similarity, we will refer to this process of photo- emission as Cerenkov emission in a vacuum. In order to derive an expression for the rate of energy loss by this process, we must impose a cut-off on the radia- tion energy spectrum?namely, we assume that no photon can carry away from the tachyon enough energy it ic im rincei I-N1F. in en tiJx, Declassified in Part - Sanitized Copy Approved for Release 2014/01/09: CIA-RDP79-00999A000200010093-3 Declassified in Part - Sanitized Cm is flat from zero to the energy of IT tachyon?that is, all photon energies from zero 'to the full energy of the tachyon are equally probable. The energy-loss rate per unit path length is dE 2r2Z2e2 E2 ds h2,2 ? for a tachyon of charge Ze and energy E. With this expression it is possible to determine the distance a tachyon would travel before its energy dropped to less than 1 eV. Surprisingly, in- dependent of the initial energy, the distance is very small. Typically, if the initial energy is approximately 1.1c2, the distance is a fraction of a milli- meter! This result has an important experi- mental consequence. Because these objects lose all their energy so quickly, it is highly unlikely that they would have been observed in any previous experimental studies. Standard de- tection devices such as scintillation counters or bubble chambers would not have found tachyons. All such devices require a particle to deposit energy in order to be detected. 5. Tachyons cannot be "stopped" by interactions with matter. But can they be captured by a nucleus or by an electron? If this has an appreciable probability, any experiment looking for such objects would be affected drastically. Feinberg (4) claims that it is not at all clear whether such a process could occur. We have at- tempted to estimate the magnitude of this capture effect using a fairly simple model, in which the tachy-ons, if captured, enter bound orbits around the capture centers (5). Even if all the electrons in lead could serve as cap- ture centers, the mean free path in Figure 3. Velocity addition for tachyons. If a tachyon is traveling with a velocity u in one Lorentz frame, what is its velocity in an- other frame moving at a velocity v with re- spect to the first frame? (7 ? 1)Iviluiv u ^yv V2 = ? ?)c2 = V 2 /C2) 1/2 1 t12 1 \ 1 _v2/c2. ) i(1 IUHVI)1 c2 c2 Approved for Release 2014/01/09 : CIA-RDP79-00999A000200010093-3 ASP' ? - - model, would be on the order of 104 meters! We then feel confident that the probability of capture is rather small. As indicated above, the existence of tachyons cannot be ruled out by their nonappearance in conventional par- ticle detectors. However, it is inter- esting to see what limits can be set on their production by studying ex- isting experimental data. To do this, we examined photoreactions?those induced by photons--because they are well understood, both theoretically and experimentally. We compared the total cross section for photons interacting with lead with both the sum of experimentally observed par- tial cross sections and with the the- oretical total cross-section predictions. In the low-energy region the total cross section is quite large (at 0.4 MeV, it is --,70 barns), and the agree- ment between theory and experiment is quite good: ? 2%. This small an uncertainty would still allow a very large cross section for other processes. If it were all due to ta- chyons, these measurements place an upper limit of only 1 barn on tachyon production. Our conclusion thus was that there was in principle no reason not to have tachy-ons and there was no overwhelming evidence against their existence. How to look for tachyons There are basically two types of ex- periments that can be performed to hunt for these particles. The first utilizes the tachyon's spacelike four- vector. In other words, in a reaction such as A-PB?>C4- X the momenta and energies of A, B, and C are measured. These quantities coupled with energy and momentum conservation determine the square of the mass of the X particle, without any direct observations on X. If X is a tachyon, the square of the mass is negative, enabling us to make a unique identification. The second method, suitable partic- ularly for charged tachyons, in- volves detecting the Cerenkov radia- tion emitted in a vacuum. Unfortu- nately, this technique is not easily implemented. In regions close to the production point, there will be large ? Declassified in Part - Sanitized Copy Approved for Release 2014/01/09 Face of photo' multiplier Figure 4. Schematic diagram of a charged tachyon experiment. Tachyons are produced in the lead shield surrounding the radioactive source and travel to the high-voltage plates, where they are detected by the emission of Clerenkov radiation in a vacuum (from 5). Plate system cesses. Far from the production point, in relatively low background areas, the tachyons will, in general, have radiated away almost all their energy, making detection rather difficult. For reasons of simplicity and cost, T. Alvager and I (5) chose to utilize the second technique. In order to overcome the problems just men- tioned, we made the additional as- sumption that charged tachyons in- teract with electrostatic fields. In particular, we assumed that tachyons could gain energy in the same manner as normal particles. Therefore, it would be possible to increase a ta- chyon's energy to any desired value at any point along its path. The rate of change of energy along its path is then dE22.2 z2e2 ? ? E2 Ze ds h2,2 where E is the electric field and we have assumed E uc2. The first term in this expression is the rate at which energy is radiated away in the form of Cerenkov light, while the second is the gain of energy in the field. Clearly, the tachyon will reach a stationary energy state when it is emitting energy at the same rate it is gaining. For energy levels in the few : CIA-RDP79-00999A000200010093-3 Declassified in Part - Sanitized Co fields required are only several hun- dred volts/cm and the levels are reached very qnickly--typically in a small fraclion'of a millimeter. With sta- tionary energy states of a few electron volts, the Cerenkov radiation will be partially in the visible range. The detection problem is then trivial, because standard photomultiplier tubes can be used. A schematic drawing of experimental apparatus using this technique is shown in Figure 4. A cesium 134 source (emits photons of 797 and 605 keV) was used to produce the tachyons in a lead shield surrounding the source. If tachyons were produced, they would travel through some addi- tional lead shielding and then pass between two parallel plates situated in vacuum and held at 9 kV voltage difference. The phototube looked at the region between the plates. The Cerenkov radiation is expected to be emitted at with respect to the direction of motion so that the photo- tube is located at the optimum angle. 1The electric field was chosen to place the radiation in the sensitive region of the phototube. The detection technique was rather simple; the pulse height was recorded for all events with measurable pulses. The majority of the events were triggers Idue either to dark current in the photomultiplier or to light from small corona points on the plates. Data lwere taken under various conditions? with and without the source and with and without the high voltage. The number of photons in the sensi- tive region of the spectrum which will reach the phototube per tachyon can be calculated. Since, on the aver- age, all the tachyons pass through the same field, the existence of ta- chyons should yield a peak in the pulse height spectrum. Figure 5 shows the pulse height spectrum with the io-source data subtracted and with rthe position for a tachyon peak in- dicated. Clearly, there is no evidence or abundant tachyon production. Assuming that a peak with a height pf at least 0.1 counts/sec was the Minimum "tachyon signal" detect- able in this apparatus, we found that the photoprod uc Lion cross section for tachyons in lead by 800 keV pho- tons was less than 3 X 10-3? cm2. This limit (shown i in Table 1) is valid for clin meg on thp t (41x7rIn c f Declassified in Part - Sanitized C py Approved for Release 2014/01/09 : CIA-RDP79-00999A000200010093-3 Expected position of tachyons 11 _ 1 ItliT 1 i if 1 1 I 1 if if i ?0.05 0 10 0.10 0.05 c:".; 0.00 20 30 40 Channel number Figure 5. The observed pulse-height spec- trum, showing the expected position for a tachyon peak (from 5). charge on the tachyon is too large, the stationary levels yield light which falls below the sensitive region of the phototube; if the charge .is too small, it takes a long time to reach a station- ary level, thereby greatly reducing our detection efficiency. It is inter- esting to note that the limit is valid for all masses s, since tachyons can exist with zero total energy whenever " = i2C". Although this experiment laid to rest any qualms about the existence of huge fluxes of these particles, the prospect of looking for them was quite appealing. In efforts to improve on the first experiment, we were joined by M. Davis (8, 9). The ground rules for the second-generation experiment were straightforward; it had to be inexpensive and not require a long operating time. The major problem limiting the first experiment was the relatively large counting rate due to corona discharge and to dark current in the phototube. A simple way to avoid these problems would be to use two detectors and place their signals in coincidence. This would also avoid the necessity of pulse-height analysis. A schematic drawing of the experimental setup is shown in Figure 6. The idea is the same as in the first experiment? namely, tachyons are produced in lead by 1.2 MeV photons from a Co" source and then travel through two identical detectors consisting of parallel plates in a vacuum. In order to reduce corona discharges, the plates were covered with opaque construction paper (see Fig. 7). This innovation, which proved very suc- that such values are not introduced cessful, involved an additional cost artificially by measurement errors 510 610 two detectors were counted for 104 seconds each, with and without the source. In each state, we observed 7 counts, a number consistent with the expected accidental rate. This yielded a counting rate for tachyons of less than 4.8 X 10-4 counts/sec implying that the photoproduction cross section is less than 1.67 X 10?" cm' at 1.2 MeV What does this limit mean? To a physicist, it is instructive to note that this upper limit is more than 108 times smaller than electron-positron pair production at the same energy. In terms of a mean free path for pho- tons, a photon could travel through 11,000 miles of lead before it had any noticeable probability of produc- ing a tachyon. Although these experiments were the first to address this problem, recently there have been others, employing different techniques, that should be discussed. Two bubble chamber ex- periments (70, 11) have attempted to look for tachyons using the missing mass technique. For normal particles, the square of the missing mass ? is al- ways greater than zero. For single tachy-ons, the mass squared is always negative, and when a pair of tachyons is created, the pair may have either a positive or negative mass squared. Therefore, if one examines an inter- action and calculates the mass squared of missing particles, only tachyons or tachyon pairs would appear to have negative values. Great care must be taken, of course, to ensure opy Approved for Release 2014/01/09 : CIA:RDP79-00999A0602b0610093-3 Declassified in Part - Sanitized Copy Approved for Release 2014/01/09 : CIA-RDP79-00999A000200010093-3 111.-41tal a ,..J1-111.J die given in Table 1.) Face of photo- multiplier Figure 6. A second-generation detector. Two identical devices are placed in coincidence (from 8). The first of the two experiments, by Baltay and his colleagues (10), merely looked for negative invariant masses for unseen or neutral particles. The experimenters examined reactions in which either K- mesons or antiprotons were stopped in a bubble chamber. In particular, they searched for can- didates for the following reactions: p A? + T?; K-p A? -I- T? T? p 7+7? ; p p ir?r? 7'? where T? and T? are unseen neutral particles, hopefully tachyons. This . particular set of reactions is advan- tageous as it is not necessary to make any assumptions about the interaction ? of tachyons with matter. The only assumption is that negative. values of the square of the mass are not sup- pressed. with respect to positive ones in the case of tachyon pairs. The Plate system \T+ Evacuated chamber Gamma source measurement is quite simple: the momenta of all the visible particles are measured, and the mass squared of any missing particles is calculated. The mass squared is then plotted, and all very low-mass or negative- value events are examined carefully. The data for one reaction is shown in Figure 8. There are some "tachyon candidates" in the data sample; how- ever, in all cases, a careful examination of each questionable event showed that the apparent negative values were incorrect and had been caused either by measurement errors or by addi- tional effects that had not been in- cluded in the reconstruction process (for example, scattering of one of the particles after the interaction of in- terest). The results of the re-analysis of the "borderline" events is also shown in Figure 8. The lack of ta- chyon candidates indicates that the probability of producing tachyons in these reactions is ?-,-,2,000 times less likely than producing ir? mesons. - Iret 4,?ef e -4 'I" C Figure 7. The improved detector. Note the corona (from 9). (Copyright, 1969, The The other major bubble chamber experiment, by Danburg and his colleagues (11), required the assump- tion that charged tachyons would leave tracks in a bubble chamber similar to those of , normal particles. This relies on the assumptions that Cerenkov radiation does not occur and that ionization energy loss does. The experiment consisted of a search for events in which charged pairs of tachyons are produced. Since each member of the tachyon pair can be examined, this technique should de- tect tachyons (subject to the correct- ness of the major assumption) inde- pendent of the sign of the mass squared of the tachyon pair. As in the previous experiment, no candidates survived careful re-examination, yielding an upper limit on the production cross section (see Table 1). Other techniques A slightly. different approach has been ? used by Murthy (12), at the Tata Institute.. He argues that ta- chyon production might occur . in high-energy cosmic-ray interactions? extensive air showers. Once a primary particle interacts in the atmosphere and a shower develops, the major components of the shower?electrons and photons?travel at a thereby defining the shower front. Heavier particles tend to travel more slowly and therefore arrive later than the shower front. Some early quark searches used that fact to look for heavy quarks. Tachyons, on the other hand, would arrive before the showers. For example, if a tachyon were pro- duced at 2 km above the surface, it would arrive ,usec before the shower front; the full range of the time difference is 0 to 20 usec. The experiment consisted of trigger- ing on a potential tachybn signal and waiting for ,-,20 usec for the arrival of an extensive air shower. The po- ? tential tachyon signal could be created by charged tachyons radiating Ceren- kov light in a vacuum or by either neutral or charged tachyons inter- acting with liquid scintillator. The total rate for the arrival of showers following such potential tachyon sig- nals is completely accounted for by accidental coincidences. In addition, Declassified in Part - Sanitized Copy Approved for Release 2014/01/09 : CIA-RDP79-00999A000200010093-3 Declassified in Part - Sanitized Copy Approved for Release .andom,cointidences. Since there is :vidence for tachyon production, the Imhimit on tachyon production in exten- i Five showers relative to electron ;um?roduction is -4 to 10-5. ,voul :mbN. fairly interesting search for tachyon- ticleike objects has recently been corn- thpleted by Bartlett and Lahana (7). nee,in order to justify their search, they doe-tote that ordinary particles are either areientral or electrically charged and h-s ihat those that move at v = c are eaeleutral. Therefore, there is a certain n Rinrnetry if tachyons are either neu- diral or magnetically charged. The Tee.xperiment, then, is a search for inthtnagnetic monopoles that are traveling ,arefaster than c. Although this appears into be a rather uneconomical ap- qveproach?namely, to hope not only athat there are tachyons but that they brn,are monopoles as well?there are some theoretical arguments (13) that charged tachyons would, in fact, f'exhibit all of the properties of mag- netic monopoles. ha thThe experiment is analogous to the taearlier searches with the appropriate hinterchanging of t and H fields. -is-The two phototubes detect the ae- larrenkov light from radiation in the [ieranagnetic field and are sensitive to ajo!objects with magnetic monopoles -on,between 1/10 and 4 times the size of ca Dirac monopole. Working with anta 20,000 curie, Co" source, the re- tonsearchers found no candidates. This ar.y-ields extremely good limits on the arlproduction cross sections, which were to/typically less than 10-36 cm2. het rs.An experiment (74) has been con- ro.ducted at Brookhaven National Labo- , itratory to search for the emission of thenegative-energy tachyons by protons. theIn the reaction proton proton + tachyon, the emission of a negative- energy tachyon appears the same as er- the absorption of a positive-energy 1-1c1 one. A proton at rest would therefore 1/al suddenly move if the reaction has Co- occurred. This process can be searched 'ed for by examining a bubble chamber 11.. with no incident particles; any pro- er: tons that were suddenly "inspired" ? to move would leave tracks. The he experiment yielded many such tracks?all of which could be ex- plained by gamma emission from )y; radioactive materials near the bubble ? chamber. Taking one event as an upper limit, the researchers found Number of events/0.002 (13eV)2 150 100 50 2348 events ? 2014/01/09: CIA-RDP79-00999A000200010093-3 emi (mr.) 2 ?0.15 ?0.10 ?0.05 (n1.?)2 in (BeV)2 15 10 0 0.05 Remeasurements of events with m12--4.0.014 ?0.15 ?0.10 ?0.05 0 (m10)2 in (BeV)2 Figure 8. Results of a search for neutral tachyons and tachyon pairs. The upper graph indicates some tachyon "candidates" greater than 102' years. Similar life- times can also be obtained from a consideration (14) of experiments on baryon conservation and measure- ments of the heat flux from the earth. Philosophical considerations All of these experiments have one major limitation: since they produce upper limits on the production and/or existence of tachyons, they never seem to satisfy the skeptic. The skeptics?or true believers?give arguments which ask: "But suppose the cross section is really only a factor of ten below the current limit?" Usually there is no satisfactory answer to such ques- tions, although the skeptics should be encouraged to perform the experi- ments themselves. However, there does exist a method which, in princi- , Declassified in Part - Sanitized Copy Approved for Release 2014/01)09 0.05 0.10 which do not stand up to a refined analysis, as shawn in the lower graph (from 70). argument is presented as a philosophi- cal end to this discussion of tachyons. L. Parker (13) suggests that there are two types of coordinate systems: (1) the normal, or subluminal, frames in which ordinary particles behave prop- erly and tachyons travel with Ivi > c; and (2) superluminal ("faster-than- light") frames?relative to which tachyons behave as normal particles. ? In a world with only one spatial di- mension, it can be shown that (1) in the superluminal frame, tachyons have real masses, and in such frames it is possible to construct a quantum field theory completely similar to that for subluminal particles in subluminal systems; (2) the mathematical trans- formations involved in going between the frames are entirely symmetric. Therefore, in a superluminal frame, : CIA-RDP79-00999A000200010093-3 Declassified in Part - Sanitized Copy Approved for Release 2014/01/09 : IA-RDP79-00999A000200010093-3 Table 1. Summary of searches for tachyons. Type of search Comments aerenkov radiation- photomultiplier .le < Z < 2e Refer- Typical results ences Photoproduction cross section < 3 X 10-3? cm2; 800 KeV photons on lead (5) aerenkov radiation- .5e < Z < 1.9e photomultipliers Photoproduction cross section < 1.7 X 10-"cm2; 1.2 MeV (8) photons on lead Missing mass squared- neutral bubble chamber K- and stopping typical result: Probability for the reaction: K- p A? tachyon Probability for the reaction: K- p A? + Tr? < 2 X 10-3 (10) Missing mass squared- Assume charged tachy- bubble chamber ons leave tracks in bub- ble chamber K- interactions at 2 GeV/c Production cross section for charged tachyon pairs < 2 X (11) 10-" cm' Cosmic ray--extensive air showers Tachyons arrive before Occurrence of tachyons in cosmic ray showers < 10-4 shower front Occurrence of electrons in cosmic ray showers (12) Tachyon-like magnetic Interchange E and H monopoles Photoproduction cross section on lead < 6 X 10-37 cm' on H2O