A search for monopoles and tachyons at ground level was carried out using an arrangement consisting of an ionization calorimeter and two hodoscope detectors. No clear evidence for these particles was obtained. The flux of monopoles with velocities beta approximately  0.01 is found to be less than 5.1 x 10 to the minus 13th power square centimeters s(-1) sr(-1) (95% cl.). The upper limit on the tachyon flux density is set as a 6 x 10 the minus 9th power particle/square centimeter event

Ashitkov, V. D.

Kirina, T. M.

Klimakov, A. P.

Kokoulin, R. P.

Petrukhin, A. A.

English

NASA Technical Reports Server

222
' lIE6.1-3
RESULTS OF A SEARCH FOR MONOPOLES AND TACHYONS
IN HORIZONTAL COSMIC RAY FLUX
Ashitkov V.D., Kirina T._., Klimakov A.P.,
Kokoulin R.P., Petrukhin A.A.
moscow Physical Engineering Institute, Moscow 115409, USSR
Abstract.A search for monopoles and tachyons at ground
level has been carried out using an arrangement consis-
ting of an ionization calorimeter and two hodoscope de-
tectors. No clear evidence for these particles has been
obtained. The flux of monopoles with velocities _ _IO -2
is found to be less than 5.1_10 -_3 cm-2s"sr"(95% c. 1. ).
The u2per limit on the tachyon flux density is set as
6 _I0_ particle/cm2event.
I. Introduction. In spite of the fact that monopoles and ta-
c-_yons are absolutely different objects the search for these
particles has been conducted using the same experimental ar-
rangement. A detailed description of the detector used in
the experiment, the motivation and first results have been
published elsewhere [I-3]. The arrangement consisted of a
six-layer ionization calorimeter and two G.-M. counter hodo-
scope detectors, and
i) events in the calorimeter with approximately equal
ionization of more than 100 cascade particles obser-
ved in all six layers have been selected as monopole
candidates ;
ii) muon induced cascade showers in the calorimeter were
used as reference events to search for preceding
particles (tachyons) produced in high energy colli-
sions in the upper atmosphere.
_Present paper sums up results obtained during five ex-
perimental runs .in 1980 - 1984. The total observation time
exceeded 2.2210" hours so available statistics have been
doubled in comparison with the publications at the previous
conference [2,3] .
2. Monopole. If the massive monopole would t_erse the ca-
lorimeter---_e ionization in all six layers would be approxi-
mately equal. In our experiment trigger signals were genera-
ted when ionization in any three layers of the calorimeter
exceeded a threshold level 80 cascade particles (c.p.) with-
in the time gate of _O_s. The events with the measured
ionization _ _0 c.p. i_all layers of the calorimeter and
with the angle between the particle trajectory and calorime-
ter axis less than 55" have been selected for the analysis.
The ratio of the maximum measured ionization to the
average one '_was used as a quantitative criterion of equal
ionization :
6
(1) R = Imax/(_Ij/6) , where j is the layer number.
https://ntrs.nasa.gov/search.jsp?R=19850027816 2020-03-20T17:10:09+00:00Z
223
HE6.1-3
In a real experi- M ' ' '
ment even in the case
of equal ionization R
may appreciably devi-
ate from the unit due _0 Fig.1to measurement errors.
We estimate the upper
limit of r.m.s, ioni-
zation measurement er-
ror as 20%. Assuming
that errors followed
to the log normal dis- 20 , _i *_!
tribution we calcula-
ted the distribution
of events as a functi_ ,
I
on of R for the case
of uniform ionization l-r
along calorimeter ,_ :_.._::.._.--.-:.;.
:".:'.%:;.._ /-_ T_'_!': .*.,':, :....
depth (dashed curve in ' ""
Fig.1 ). 0
1.0TRcr 2.0 3.0 &o R.
The observed dis-
tribution for slx-layer events with average ionization of
more than 400 c.p. (solid histogram in the figure) drastica-
lly differs from that for uniform ionization. We suppose
that all these events are cascade showers. To estimate the
background from the showers the Monte Carlo simulation of
slx-layer events was performed (broken line ). A good agree-
ment of this calculation with experimental data gives the
evidence that all slx-layer events represent a background.
. The ionization from a single heavily ionizing particle
must be localized in one or two adjacent chambers in every
layer. This fact permits to cut the shower events due to
their wide transversal ionization distribution. The events
" selected in accordance with this additional restriction are
presented by the shaded histogram in the figure. Finally,
hodoscope information was used to reject shower events which
are often accompanied by plural fired counters in the exit
detector.
In the previous paper [2] we used Rcr= 4.5 to separate
possible monopole events from shower ones. However, calcula-
tions showed that the optimal value of Rcr is equal to 4.3
which corresponded to monopole selection efficiency _>65%.
With the above criteria no monopole candidates were
found. Taking into account the geometric acceptance (44.3
m2sr), available operation time (8_I07 s) and selection ef-
ficiency (0.65) we have estimated the upper limit of mono-
pole flux from the top hemisphere as 5.1x10"_c_2s"sf_(95%
c.1. ). According to theoretical calculation for monopole
energy loss [4] the ionization range _I00 c.p. corresponds
to monopole velocities _ >_IO"2.
224 HE 6.1-3
3. Tachyon. The situation around the bachyon hunt is rather
complicated. There are almost no theoretical predictions
concerning the interactions of these superluminal particles,
therefore it seems reasonable to use every possible means to
found bachyons. Our experiment is based on the assumption
that tachyons are very common particles : i) bachyons may be
produced in high energy collisions of primary nucleons in
the atmosPhere or in the decays of any secondaries; ii) bhe_
can arrive to and be detected on the Earth surface; and iii)
the efficiency of their registration by G.-M. counters is
not equal to zero.
Tachyons may be identified as particles which arrive
the observation point earlier than other particles produced
in the same interaction• High energy cascade showers initi-
ated by muons in the ionization calorimeter were used as
triggers while potential tachyons were detected by hodosoope
only. The number of triggering muons was ~8_04 for the mi-
nimal cascade shower energy ~20 GeV. The effective energies
of muons and those of primary nucleons corresponding to this
threshold were ~100 GeV and ~1 TeV, respectively.
The time and arrival direction information from hodos-
cope detectors was recorded in the tlme interval T =26 ms
before the trigger, but the delaying events were also analy-
sed for the comparison. Only preceding and delaying pamtlc-
les wlth trajectories parallel to those o£ triggering muons
have been selected. The observed events ar.epresented by
points in the (aT- cos e) diagram (Fig?2). Th.ez_ is no app-
arent difference between the preceding (AT <0) and delaying
(AT > O) particles.
The fly-off tlme between the relativistic muo_ and pre-
ceding or delaying particle depends on the particle velocity
and the distance from the primary nucleon interaction
altitude to the observation point L, which in its burn de-
pends on the zenith angle G and the interaction depth in the
atmosphere x: AT = (1/_ - 1/c)L(e,x). (2)
I
i i I ...... ! • ! I
C/I I -"-:;:: I •
. .. . , ,_-_:_ •
• • • I ,::'1".:.:.1_ " .
• • • / I---I'--I ' " • ,,,
0.3 ' '::'_::'"_• " " •
I ...... "" • " •
.... ., ,::_:.-:, _.. . •
• "'"" .: • /"l"-'[:-"_ "_ "" " "
• " ,': .../ ;,::iE::'_,',., "' .... ,
o2 , : a . , ,_::_, ',.... , I
• • / ,. :::'1:-'- _ , •.• "1
• • • ee • I • le e. ..... e% • e%.e • • • e • •
• ,. , .::1=: • • ,.• • /
• " , 4 • & 0"I "-'[::: _0 _. • 2 • , |
0.1 " /" / " ::'L::'." _. "'. " " " 1
p,_ S :::1::: % k el
• e" / ...... k k •
oo ..... ,, , --. I
Flg.2
-2 -1 0 1 2 AT, ms
liE 6.1-3
225
Since in our experiment the large zenith angles (e > 60° ) ate
accessible, values of L were calculated for x = 12.6 g/cm 2
depth along the particle trajectory. Assuming a 120 g/cmZnu-
cleon absorption length, this value corresponds to 10% atte-
nuation of primaries so 90% of tachyons would be produced at
such or shorter distances. The curves fland 2 in the figure
give the angular dependence of _T for preceding particles
with velocities _==o and _ = 2c correspondingly. Since the-
re are no predictions about the definite tachyon velocity we
considered the case of arbitrary velocities, i.e. all events
under the curve fl.The observed number of these events was
39. The curves 3 and 4 are dr_wn symmetrically for the com-
parison. The number of delaying particles under the curve 3
was 47. The expected value of the background was calculated
considering : i) area un-
, , . , der the curve I, ii) an-
G _ gular distribution of mu-
i0_ Q _Tm ons, and iii ) the total
number of events in 26 ms
interval, and was equal
Q m_ to 37.0 + 1.7. The sumed
_07 coliecti_g area of the
(_ m_n Q mvn hodoscope detectors cons-
o tituted 3.O_10_cm _.Taking
_i0-' pncs_.tdata into account the hodos-
_m cope efficiency (of about
O.8) the upper limit of
the density of tachyons
_0" ' ' ' J ' associated with high ene-
I0_2 10_s I0_ lO_S EI_,_'V rgy muons was estimated
Fig.3 as 6_10"sparticle/cm 2event.
The direct comparison of our results with other sear-
" ches for tachyons is complicated since only few authors give
quantitative limits. Therefore we estimated upper limits of
tachyon densities using the published experimental data[5-9]
• as follows :
(3) _ 3 "_n'AT'N'/ S.N,
where n is a background rate; S is the area of the tachyon
detector; _ is the number of triggers; AT = 100 _s is the
. preceding time interval for the vertical direction (_ = =o ,
x = 12.6 g/cm2). Results of these calculations are presented
in Fig.3. Ciphers near the bars correspond to the reference
numbers.
I. V.D.Ashitkov et al.Izv.AN SSSR,Ser.Fiz.,@5, fl319 (1981)
2. V.D.Ashitkov et al. Proc.fl8th ICRC, _, 65 (1983)
V.D.Ashitkov et al. Proc.18th ICRC, _,fl29 (1983)
S.P.Ahlen,K.Kinoshita.Phys.Rev.D, 2__66,2347 (1982)
5. P.V.Ramana _urth_. Lett.Nuovo 0ira.,!, 908 (_97fl)
G.R.Smith,S.Stan il.Ca.J.ehys.,> 1280(1977)
7. _l.V.Emery et al. Proc.fldth ICRC, 2, 2@86 (1975)
8. D.J.Fegan et al. Proc.qdth ICRC, _, 2480 (1975)
9. G.C._ac_eill, D.J. Fegan. Proc.fl8th ICRC, 5, lflO (1983)


Results of a search for monopoles and tachyons in horizontal cosmic ray flux

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