Energetic delayed hadrons in air showers with electron sizes in the range 10 to the 6th power to 10 to the 9th power were studied by observing the delayed bursts produced in the shield of nine square meter scintillation detectors in the Chacaltaya air-shower array. The frequency of such delayed burst is presented as a function of electron size, core distance and sec theta

Hagiwara, K.

Inoue, N.

Kakimoto, F.

Kaneko, T.

Martinic, N.

Miranda, P.

Siles, L.

Suga, K.

Tsuchimoto, I.

Yoshii, H.

English

NASA Technical Reports Server

283
HE 6.2-9
Energetic delayed hadrons in large air showers observed
at 5200m above sea level
Kaneko, T.
Department of Physics, Okayama University, Okayama 700, Japan
Hagiwara, K.
The Institute of Physical and Chemical Research, Wako, Saitama
351, Japan
Yoshii, H.
Faculty of General Education, Ehime University, Matsuyama 790,
Japan
Martinic, N., Siles, L. and Miranda, P.
Instituto de Investigaciones Fisicas, Universidad Mayor de
San Andres, LaPaz, Bolivia ,
Kakimoto, F., Tsuchimoto, I., Inoue, N. and Suga, K.
Department of Physics, Tokyo Institute of Technology, Meguro,
Tokyo 152, Japan
ABSTRACT
Energetic delayed hadrons in air showers with electron sizes in the
range 106`0 to 109.0 have been studied by observing the delayed bursts
produced in the shield of nine 4m 2 scintillation detectors in the
Chacaltaya air-shower array. The frequency of such delayed bursts is
presented as a function of electron size, core distance and sece.
I. Introduction
The Bolivian Air Shower Joint Experiment (BASJE) group carried out a
series of measurements of the arrival time distributions both of muons in
air showers with primary energies above lOlTev and of atmospheric Cerenkov
15 " 17
light from air showers with primary energies from 5x10 eV to 2x10 eV in
the Chacaltaya air-shower array (550gcm -2 atmospheric depth, 5200m above
sea level). On the basis of these measurements, we concluded that the ion-
, gitudinal developments both of muons and of electrons at the early stages
are consistent with those expected from very high multiplicity models of
particle interactions(1)(2). This conclusion is supported by measurements
of the arrival time distributions of muons and of atmospheric Cerenkov
light in the Akeno air-shower array (930gcm -2 atmospheric depth, 900m
above sea level) by the Tokyo Institute of Technology(group using thealmost same apparatus as used in the Chacaltaya array 3)(4).
Furthermore, high-energy delayed hadrons in air showers have been
studied in the Chacaltaya array to examine whethe r the character of themul-
t tiple production of nucleons and anti-nucleons in high-energy interac-
tions is also consistent with this conclusion, and to obtain an informa-
tion on unknown heavy particles which may be produced in high-energy
interactions. These delayed hadrons were observed as delayed bursts pro-
duced in the shield of nine 4m 2 scintillation detectors in the Chacaltaya
array.
In this report frequencies and delay time spectra of these delayed
bursts are presented for air showers with electron sizes in the range
106.0 to 109.0 .
*Present addres: Department of Physics, Meisei University,
Hodokubo 337, Hino-shi, Tokyo 191, Japan
https://ntrs.nasa.gov/search.jsp?R=19850027832 2020-03-20T17:09:42+00:00Z
284
HE 6.2-9
2. Experimental
The observation started in May 1982. The shield of detector is com-
posed of 231gcm -2 of galena (PbS ore), 132gcm -2 of concrete and 23gcm -2
of lead. The signal from a 5in fast photomultiplier (Philips XP2040) in
each detector was fed to an adding circuit. This combined signal was
stored in a 100MHz storage oscilloscope (Tektronix 466) by local trigger
signal generated when at least 7.0 particles passed through an unshielded
0.83m2 detector just above the central 4m 2 shielded detector (this trig-
ger level was changed to 3.0 particles from October 1982) and at least
3.5 particles passed through five shielded detectors'out of nine. When
this local trigger signal coincided with a master signal from the array,
which observed an air shower with electron size above 106.0 , the stored
signal was photographed. The time response of the whole system was 4.5ns
in rise time between 10% and 90% of the signal and 12ns in full width at
half maximum (FWHM).
3. Analysis
About 12,400 showers with electron sizes (Ne) above 106.0 and secO
(e: zenith angle) from 1.0 to 1.8 were observed until October 1983.
The delayed burst produced by a high energy hadron was picked up
primarily when the burst was recognized as a separate delayed peak in the
signal. Moreover, in order to avoid a contamination of apparent delayed
signals due to fluctuation in the arrival times of muons, following cri-
teria were requested for further screening:
(i) The burst size (nb) is larger than 15 particles.
(2) The value of FWHM of the delayed signal is shorter than 20ns.
Since the number of particles was measured simultaneously using a
16in photomultiplier (DuMont K1328) in each 4m 2 scintillation detectors,
the signal was accepted as the delayed burst finally when the number of
particles contained in the separate delayed peak wasequal to the number
of particles of burst recognized from the pattern Of the numbers of par-
ticles measured in nine detectors within the uncertainty. The delay time
of the burst was measured from the particle front in the photograph.
The distribution of sizes of bursts produced by hadrons with ener-
gies E (GeV) were already calculated for the BASJE shielded detector(5)
6). And the average nb is given by E/I.0GeV.
The delayed bursts were classified by Ne, sec0 and core distance (R)
into bins whose ranges were 0.5 in igNe, 0.2 in sec8 and 50m in R, res-
pectively.
4. Results
Since the frequency of bursts is almost independent of secO from 1.0
to 1.8, the results are presented by combining all of data in each bins
of sec0. Figure 1 shows an example of delay time spectra of the bursts.
The frequency decreases monotonously with delay time. IN figure 2 the
frequencies of delayed bursts are presented against electron sizes in
three bins of core distances. As is seen in the figure, the frequency in-
creases monotonously with electron size except for bursts with nb larger
than 15 in air showers with Ne larger than 108 in figure 2(a) and 2(b),
where the first peak in the signal arising frommuons is high and the
tail obscured the delayed peak arising from the burst. The frequencies
shown in the figure were compared with those estimated from the calcula-
tions on delayed nucleons and anti-nucleons made by Grieder(7) with a
rising cross section of hadrons and an increasing multiplicity of nucle-
285
HE 6.2-9
ons and anti-nucleons. In the present estimation, the fluctuation in sizes
of bursts from hadrons with a given energy was taken into account by re-
ferring to the calculation made by Rappaport(5). The frequencies of de-
layed bursts observed in the present experiment are higher than those
estimated at electron sizes larger than 107 , and the dependence on Ne is
steeper than that estimated. At present, the dependence of multiplicity of
nucleons and anti-nucleons on energy is being examined to explain the
frequencies of observed delayed bursts.
Figure 3 shows a diplot of the burst sizes and the delay times of all
delayed bursts in the present observation. Seven delayed bursts with nb
larger than fifty particles and the delay times longer than 50ns were
found. Whether these bursts with larg e sizes and delay times are reason-
ably explained asarising from nucleons and anti-nucleons is an important
problem and is being carefully examined.
References
(I) F. Kakimoto et al: J. Phys. G; Nucl.Phys. 5(1983)339.
(2) N. Inoue et al: J. Phys. G; Nucl. Phys. 11(1985)669.
(3) F. Kakimoto et al: HE 4.7-4 in this Conference
(4) N. Inoue et al: J. Phys. G; Nucl. Phys. i__i(1985)657.
(5) S. A. Rappaport: PhD Thesis, M.I.T. (1968)
(6) H. V. Bradt and S. A. Rappaport: Phys. Rev. 164(1967)1567
(7) P. K. F. Grieder: Riv. Nuovo Cimento _(1977)i and private communi-
cation on the calculations at altitude of 3000m and 5000m.
lO_l )shower. 36_'iOns i0. I /shower" 36_'lOnsi I ! I ! !
(a!)
10-; _ I0"z
. ..... .
_ 1'" "I
10-3 (,( 10-3
0
10-_ 10-4
+ Z
- lO"5 I l ) 10-5 I ! t
0 50 IO0 15(1 50 IO0 |50
Delay time (ns) Delay time (ns)
Figure i. Delay time spectra of bursts with burst sizes larger than 15 in
(a) and larger than 30 in (b) for air showers with electro n sizes from
107.0 to 10 ?.5 and core distances from 50m to lO0m.
286
HE 6.2-9
'shower .36m 2 /.qhower .36m 2
1 | , i i ' " 1 | ' _ I I _ I ' ' I
(a) (b)
4J
io-I H
0 0
z
T
i0-3 . , I I ,. I , , . I0"3 ' I ! I , I m . I ,
107 108 109 106 107 108 109
Electron size Electron size
1/sh_we_'_- _2_6m. I ' ' ' '
Fisure 2. Frequencies of bursts with
i (c) delay times longer than 30ns and with
burst sizes larger than 15(_) andT
_ larger than 30(_) against electronioq
sizes at core distances of 50-100m(a),
q_m I I lO0-150m(b) and 150-200m(c) .o10_: ,Fisure 3. Diplot of the burst sizesand the delay times for air showers
withNelarger than I06"0, seceof 1.0
z -1.8 and core distances smaller than
i0-_. , I , , ! , , I , 200m.
107 108 109
Electron size
200 I I i I I l
150 . •
N i00 • ,,
oo m,B
4-J •
; :;.t::. ••
50 ,,6tam'*. |. *,
-"_"-_'" Z • .
Z_ft31"Wl'O * :Id"_ Q • •
• .... •
o t , , , i .,I , t
so mo zso 2oo 2so 30o
F__igu_¢ 3. Delay time (ns)


Energetic delayed hadrons in large air showers observed at 5200m above sea level

Energetic delayed hadrons in large air showers observed at 5200m above sea level

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