Periodic signals from Cygnus X-3 in the ultra high energy range were recently reported by air shower arrays and attributed to gamma rays. Although gamma rays are expected to produce muon-poor showers, the preceding observations have stimulated similar studies based on underground muons. Two groups have claimed a significant underground signal coming from Cygnus X-3. The results are, however, extremely difficult to explain in the present framework of particle physics, and clearly need confirmation. The preliminary results obtained from the Frejus underground detector during its first 16 months of operation (March 1984 to June 1985) are presented

Bareyre, P.

Barloutaud, R.

Becker, K. H.

Behr, L.

Berger, C.

Bland, R. W.

Chardin, G.

Daum, H. J.

Degrange, B.

Demski, S.

English

NASA Technical Reports Server

465
SEARCR FOR A PERIODIC SIGNAL FROM C_O_US I-3 USIM_
MUONS OB3ERVEn UNDEROROURD IN THE "FREJUS" DETECTOR (48OO _we)
P. BAREYRE (4), R. BARLOUTAUD (4), K.H. BECKER (5), L. BEHR (3),
C. BERGER (1), R.W. BLAND (3), G. CHARDIN (4), H.J. DAUM (5),
B. DEGRANGE (3), S. DEMSKI (5), G. DEUZET (2), L. DI CIACCIO (4),
B. DUDELZAK (2), P. ESCHTRUTH (2), n. EDMUNDS (4), J. ERNWEIN (4),
G. GERBIER (4), R. HINNERS (5),A. HOFFMANN (1), M.A. JABIOL (4),
s. JUU_AN (2), w. _0HRS (5), W. KOLTON(4), B. _UZ_fX (5)+ O. LAL_
(2), F. LAPLANCHE (2), C. LONGUEMARE(2) , R. MAYER (5), H. MEYER (5),
L. MOSCA(4), L. MOSCOSO(4), U. SOVYES-_C (3), _. OST_aSS(5),
C. PAULOT (2), J. PETERS (5), F. RAUPACH (1), Ph. ROY (2), G. SC_MITZ
(_), M. SCHUBNZLL(5), P. SZmU (3), a. SZXL_Z (2), J. _IERJUN_ (5),
S. TISSERANT (3),J- TUTAS (I) and B. VOIGTLINDER (1).
(I) I. Phys. Institut der Techn. Hochschule, Aachen, Germany.
(2) Laboratoire de l'Accdl_rateur Lin4aire, 0rsay, France.
(3) Laboratoire PNHE, Ecole Polytechnique, Palaiseau, France.
(4) D4partement de Physique des Particules El6mentaires,
Centre d'Etudes Nucl4aires de Saclay, France.
(5) Universit_t- Gesamthochschule, Wuppertal, Germany.
I. Introduction.
Periodic signals from Cygnus X-3 in the ultra-high energy range
have been recently reported by air-shower arrays [I] _ they are
naturally attributed to v-rays. Although v-rays are expected to produce
muon-poor showers [2] , the preceding observations have stimulated
similar studies based on underground muons. Two groups [3,4] have
cla£med a significant underground signal coming from Cygnus X-3. Their
results are however extremely difficult to explain in the present
framework of Particle Physics, and clearly need confirmation.
We present here the preliminary results obtained from the
"Frdjus" underground detector during its first 16 months of operation
(March 1984-June 198S).
2. Site.
The "Frdjus" proton-decay detector is located in the "Modane
underground laboratory" in the middle of the Fr4jus tunnel linking
France and Italy in the western Alps, about 80 km south of the Mont-
Blanc. Figure 1 shows a sketch of the underground laboratory, whose main
characteristics are summarized in Table 1.
https://ntrs.nasa.gov/search.jsp?R=19860022037 2020-03-20T13:31:38+00:00Z
466
TABLE !
Longitude : 6.69 ° E
Latitude : 45.14 ° N
Average slant depth : 4800 mwe
(all muons)
!
Average slant depth : 5010 mwe
(Cyg. X-3 direction)
Average threshold for muons : 3 TeV
Muon angular deviation in
the rock (average) : I°
Muon rate : 4.2 m-2 day -I
Primary cosmic ray energy range: I0 - I05 TeV
Dimensions of the main hall : 30m x 10m x llm
L E h
/
,%% /"
Figure I ;
Modane underground
Laboratory.
467
3. The detector:
The "Frdjus" proton -decay detector (l_.3m x 6m x 6m) consists
of a fine grain flash-tube calorimeter (0.9810v flash-rubes) triggered
by a set of 113 vertical Geiger planes. The trigger planes (each
including 352 wires) are interspersed between flash-tube sections every
I0.8cm, thus ensuring a good trigger efficiency for muons. Flash-chamber
planes as well as Geiger planes are alternatively made of horizontal
tubes (providing the side view of an event) and of vertical rubes
(providing the top view), as is sketched in figure 2. The flash-tube
section (Smm x 5ram) and the close spacing between f]2_sh-chamber planes
(3ram of iron) lead to a high spatial resolution (2ram on a muon r_ack).
The projected area, averaged over all muon directions is 96 m-. The
total weight is 912 metric tons. The detector orientation is known with
an accuracy of 0.2 °.
-__ _ Figure 2 :
•-_ General structure of
the detector.
The experiment started in March 1984 with only a part of the
detector. The experimental set-up was completed at the end of June 1985.
The data presented here have thus been taken in a detector with an
increasing size. They mainly consist of 106 000 single muons, 3100 muon
bundles (figure 3) and of 22 vertex-contained events, all of them being
compatible with neutrino interactions (figure 4).
468
Figure 3 : A muon bundle
_t0
-
,. ..:--. ; ;" . .*
,"l_l_c_?:'":,?
"" .:' -, _.. .... .
;i'.'
Figure 4 : A neutrino event
469
4. Search for a periodic signal from Cy_nus X-3
In order to ensure a good direction measurement (a few
mi.lliradians), muons stopping in the detector as well as muons crossing
less than 8 detection planes per view were removed from the sample of
single muons. One is thus left with about 90 000 muons for which the
average trigger efficiency is 96_. For such muons, the angular error on
the source direction is dominated by the average angle of multiple
scattering in the rock. Taking into account the small error on the
arrival time of the muon (no precise clock being available to date), a
conservative estimate of the angular resolution is 1.5° .
The present data are quite comparable to those of the NUSEX
experiment [4] in the Mont-Blanc tunnel. Sites have nearby geographical
positions and similar average slant depths_ both experiments have the
same angular resolution. For these reasons, we first follow the NUSEX
analysis and select those muons pointing back to Cygnus X-3 within ±5°
in right ascension and ± 50 in declination. This leaves us with 177
events, a statistics also comparable with that of NUSEX. No particular
accumulation in the vicinity of the source is observed in figure 5. A
possible signal can only be extracted by using the time structure
expected from the X-ray light curve, following the ephemeris of Van der
Klis and Bonnet-Bidaud [5] - The phase relative to the X-ray period was
calculated taking into account its time derivative [5] "and corrected
for the effect of the earth orbital motion.
In order to check that no distortion of the phase histogram was
induced by our apparatus or by the shape of the mountain, 6840 events
within the same band in declination as the 177 selected events (Cygnus
X-S ± 5°) but with no restriction in right ascension were considered.
Their phase distributiop shown in figure 6 is found almost uniform, and
yields an off-source background in _he 10° x I0° window around Cygnus
X-3 of 190 events, which is compatible with the number (177) of selected
events. The phase distribution of these events is shown in figure 7. The
most populated bin is the phase interval [0.6-0.7] containing 30
events, 19 being expected from a flat distribution. In the hypothesis of
a uniform background, this represents a fluctuation of 2.5 _ only.
Moreover, structures of similar statistical significance can
emerge if one selects an off-source window, keeping the same mean
declination but shifting the mean right ascension. This is shown in
figure 8 in which a shift of 30° in right ascension with respect to
Cygnus X-3 has been chosen. For this reason, it is not possible to
consider the structure in figure 7 as a definite signal.
Since our angular error is much smaller than the preceding
window size, more restrictive conical windows have been chosen, with
respective half opening angles 5° and 4° , The corresponding phase
histograms are shown in figure 9. The phase interval [0.6-0.7 ] is still
the most populated one, but the statistical significance of the excess
of events with respect to background is not increased.
470
• •
• °.
,, :"
-- C'
._ • .
_ -
°
°.
. ,°
t ° • °
i
I I I
304 306 305 3_0 312
Right ascension
Fisure 5
900 -
800
700 -
600 - '
500 - Detta of Cygnus
LO0 X3 +-5 °J
All alphas,300
828Levents
200- (before_s)
100 -.
0 , I I J I
0 0.2 O.Z, 0.6 0.8 1
471
EVEHTS
3S
.:
FF'E..ll.l'_=. r SO _:_k'_
I
L.'-.
............_........................i
14
EL_EI.ITS
36
" FRE;JUS
i A i , I !
.20 AO .60 .80 1.00
CYGNUS X3 PHASE
ZI ..................................................
Figure 7
14
.20 .4') .GO .80 L00
p_._,.b,, (ci_hC ascension of
472
HTPIES EHTP.IES
30 ' ' ' ' 20! , , , ,
m
_4 16
13 17.
6 4:'
I I I I I I I I
.ZO .40 .60 .£0 100 . --"0 40 60 80 1,30
PHASE PHASE
r- : 5 a
r -- 4
Figure 9 : Phase histograms with conical windows.
47a
5. Conclusion
With the same window in right ascension and declination as the
one chosen by the NUSEX group and a similar statistics, we find a phase
histogram which is still compatible with a flat distribution, the most
populated interval [O.6-0.7] being thus interpreted as a 2.5
fluctuation. Of course, a signal is not excluded but it should be
noted that the NUSEX peak was found in the nearby phase bin [0.7-0._]
Our statistics should be increased by a factor of 4 within Z years.
However, the source is suspected to vary with time [6] and it should be
kept in mind for the comparison of the NUSF_ and Fr4jus data that the
respective observation epochs are different.
References
I. Proceedings of the 19th ICRC, La Jolla, USA (1985), Vol. I, P.59-127.
2. T. Stanev and Ch. Vankov, Proceedings of the 19th ICRC, La Jolla USA
(1985), Vol. 7, p. 219.
3. H.L. Marshak et al., Phys. Rev. Left. 54 (1985) 2079.
_. G. Battistoni et al., Phys. Lett. 155B (1985) 465.
5. H. Van der Klis and M. Bonnet-Bidaud, Astron. Astrophys. 95 (1981)
L5.
6. A. Lambert et al., Proceedings of the 19th ICRC, La Jolla, USA
(1985), Vol. I, p. 71.


Search for a periodic signal from Cygnus X-3 usingmuons observed underground in the Frejus detector (4800 mwe)

Search for a periodic signal from Cygnus X-3 usingmuons observed underground in the Frejus detector (4800 mwe)

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