It is proposed that the fireballs invoked to explain the Centauro events are bubbles of a metastable superdense state of nuclear matter, created in high energy (E is approximately 10 to the 15th power eV) cosmic ray collisions at the top of the atmosphere. If these bubbles are created with a Lorentz factor gamma approximately = 10 at their CM frame, the objections against the origin of these events in cosmic ray interactions are overcome. Assuming further, that the Centauro events are to the explosive decay of these metastable bubbles, a relationship between their lifetime, tau, and the threshold energy for bubble formation, E sub th, is derived. The minimum lifetime consistent with such an interpretation in tau is approximately 10 to the -8th power sec, while the E sub th appears to be insensitive to the value of tau and always close to E sub th is approximately 10 to the 15th power eV. Finally it is speculated that if the available CM energy is thermalized in such collisions, these bubbles might be manifestations of excitations of the SU(2) x U(1) false vacuum. The absence of neutral pions in the Centauro events is then explained by the decay of these excitations

Balasubrahmanyan, V. K.

Kazanas, D.

Streitmatter, R. E.

English

It is proposed that the fireballs invoked to explain the Centauro events are bubbles of a metastable superdense state of nuclear matter, created in high energy (E approximately 10 to the 15th power eV) cosmic ray collisions at the top of the atmosphere. If these bubbles are created with a Lorentz factor gamma approximately equals 10 at their CM frame, the objections against the origin of these events in cosmic ray interactions are overcome. A relationship then between their lifetime, tau, and the threshold energy for bubble formation, E sub th, appears to be insensitive to the value of tau and always close to E sub th approximately 10 to 15th power eV. Finally it is speculated that these bubbles might be manifestations of the SU(2) x U(1) false vacuum excited in these collisions. The absence of in the Centauro events is then explained by the decay modes of these excitations

NASA Technical Reports Server

137 HE 1.3-15
SU(2) x U(1) VACUUMAND THE CENTAUROEVENTS
D. Kazanas, V. K. Balasubrahmanyan and R. E. Streitmatter
NASA/Goddard Space Flight C/enter
Greenbelt, MD 20771_
USA
ABSTRACT
We propose that the "fireballs" invoked to explain the Centauro events
are bubbles of a metastable superdense state of nuclear matter, created
in high energy (E ~ 1015 eV) cosmic ray collisions at the top of the
atmosphere. If these bubbles are created with a Lorentz factory : I0 at
their CM frame, the objections against the origin of these events in
cosmic ray interactions are overcome. A relationship then between their
lifetime, T , and the threshold energy for bubble formation, E ,, is
derived. The minimum lifetime consistent with such an interp_encation
is T ~ I0 -B sec, while the E,h appears to be insensitive to the value
of • and always close to E+_~ 1015 eV. Finally it is speculated that
these bubbles might be mani_stations of the SU(2) x i_(I) false vacuum
excited in these collisions. The absence of _°'s in the Centauro events
is then explained by the decay modes of these excitations.
1. Introduction. The Centauro, events (Lattes et al. 1973) are high
+
energy : 1015-i cosmlc ray events detected in nuclear emulsion chambers
at high altitudes (> 4000 m)with characteristics which defy explanation
in terms of "standard" high energy cosmic ray col'lisions and subsequent
cascading of the produced particles. The characteristics which set these
events apart from the typical events expected at these energies (= 1015
eV) are the following:
a. They are observed deep in the atmosphere (: 500 g cm-2), only a few
hundred meters above the emulsion chamber detector.
b. They have very high multiplicity.
c. They have very large mean transverse momentum, <Pt >, 3-5 times
larger than that of a typical nuclear fragmentation interaction.
d. There is a deficiency of neutral pion production.d
Direct nuclear collisions fail to account for any of the above features,
especially for the observed rate, R = 10-2 m-2sr-lyr -I, since the
probability of penetration of strongly interacting parti_cles to such
depth is negligible. It was pointed out though, that most of the above
features (multiplicity, <Pt>), could be accounted for in terms of the
explosive decay of an unknown state of matter. Bjorken and McLerran
. (1979) postulate a new metastable form of quark matter, introducing a new
component in the cosmic ray spectrum, while Kinnunen and Rubbia (1981)
argue that these events cannot be due to high energy cosmic ray interact-
ions, thus in effect agreeing with the previous authors, lh the present
" note we accept the interpretation of the Centauro events as the explosive
decays of an unknown yet high energy particle deep in the atmosphere.
However, contrary to the previous treatments, we relate the Centauro flux
to the flux of high energy cosmic ray particles at the top of the atmos-
phere, thus avoiding the introduction of a new, unknown component in the
primary cosmic ray spectrum. Then, the requirement that Centauros are
https://ntrs.nasa.gov/search.jsp?R=19850027572 2020-03-20T17:21:56+00:00Z
138 HE 1.3-15
due to the explosive decay of a bubble of a metastable superdense nuclear
matter, produced in a high energy collision on the top of the atmosphere,
leads to a relation between the formation of such a metastable state and
to its lifetime. This is done in the next section.
2. The Centauro Event Rate. In relating the Centauro rate to that of
high energy cosmic ray interactions, we shall assume that a large frac-
tion of high energy cosmic rays have interacted within 50 g cm-2 from the
top of the atmosphere, which sets the interaction height to about 21 km.
Given that the Mt. Chacaltaya detector is at a depth ~ 500 g cm-2 or a
height of _ 6 km, the bubbles of metastable matter will have to traverse
a distance of about 15 km before they decay. We further assume that any
decay at a distance dL > I00 m from the detector does not classify as a
Centauro event, because the ensuing cascade will not have the charact-
eristics of a Centauro (i.e. closeness to the detector, few_°'s). Then
if TO is the lifetime of the bubble and YL its Lorentz factor in the
laboratory frame, the decay rate of bubbles as a function of time after
the interaction will be
N(t) = mT e't/YkTo (1)
or in terms of the distance d from the high energy interaction point,
N(d) = NT e-d/CYLTo (2)
Where NT is the rate of bubble production at the top of the atmosphere.
Then the differential rate with respect to the pathlength dl within which
decays are identifiable as Centauro events is
dECd)= 1 N(d)
dl CYLTo
and the Centauro event detection rate should be
dl NT e-d/cyLTo (3)R=
Solving this relation for the rate of events at the top of the
atmosphere, NT, one obtains
YLC To ed/CYLTo (4)NT = R dl
Since we expect the formation of bubbles to have a threshold energy Ei,
NT should be the integrated cosmic ray flux at the top of the atmosphere.
with E > Ei or "
NT n K Ei"1"7 Ei"1"7 m-2 S-1= = n 1.1 104 Sr-2 (5)
with Ei measured in GeV. The factor n denotes the fraction of these
events that produce bubbles of metastable nuclear matter, which we will
presently assume to be of the order of I (n -- I). If Mb is the mass
(rest energy) of the bubble and E*h its CM energy then its Lorentz factor
in the interaction CM frame will b_
f = E*b/mb
139 HE 1.3-15
Ei 1/2
Hence the Lorentz factor of the CM will be YCM = (2T) . Consequently
the Lorentz factor of the bubble in the laboratory frame, YL, will be
YL = Mb = YCM f + (Y • (f2-I)1/2 cosO*--f (_)I/2 (6)P
Substituting equations (5) and (6) into equation (4) and solving for Ei
we obtain the transcendental equation
Ei EiR 1/2
exp (d/c (___)1/2 f To)]-o.sg (7)Ei = [n_-d-l" (T) f to
where R = 10-2 m-2sr-lyr -I is the Centauro event rate, dl = I04 cm, d =
15 km = 1.5 x 106 cm, K is defined by equation (5), and mn has been taken
as I GeV. Substituting the numerical values equation (7)_reads
Ei = [¼ 5.68 x i_ 8 Ei I/2 f t o exp (7.07 l(]5/EiZ/2f to) ]-0"59- F (Ei, to)
Equation (Ta) can be solved
7 , , , graphically by plotting the curves
! ' ' ' /f y = Ei and y = F(Ei, Tn). The
-._ . results are shown in figure I
6 _-_ where the families of curves F(Ei,
// / _'/___._ Tn) are shown as a function of Ei
I I/ /__----_ w_th fT^ as a parameter. One can
_ I /// I . ,..,_.s-'--_ distinguish two major features:
I .,/{ / _ii'°.',o-U (i) For sufficiently small valuesTo • -
4_i'f_°o_;°-s- of the parameter fTo (<I0-8) no
_. l j ii Ii d i,_.iO-,S solution to equation (7a) exists.
: ?
- _/" / / e f,o.lO"7 This means that for sufficiently
o/{ / / ff,o:iO"_'s smal1 bubble lifetimes (fT_ <10-8)
o'/ / / Cfro,lO-S not enough of them willVsurvive
/ / / deep enough in the atmosphere to
2! ,# _# , , account for the observed Centauro
4 _ e _ flux, (ii) For fT0 >10-8 there are
logEl(GeV) always two solut10ns to equation
(7a) since the curve y = Ei
Figure 1 intersects the curve y = F(Ei, to)
at two points. It is interesting to note that of these two solutions the
highest ones are always close to an energy E_ = 106 GeV for a wide range
of values of the paramter fTo, (10-6-10-8),'which corresponds to a CM
energy of-- 1 TeV.
One can of course assume that the increased penetration is due to the
smaller cross section of the"bubble". The difference is heights between
21 km (where presumably the metastable state forms) and 5 km where the
" fireball occurs and corresponds to ~ 500 g cm-2 or a cross section
> i0 times smaller than that of strong interactions. This corresponds
_o a linear dimension >3 times that of a proton and hence a Pt >3 times
that of strong interactions as indeed observed.
The assumption that the bubbles of the superdense metastable nuclear
140
HE}1.3-15
state are produced with a certain kinetic energy at the CM of the colli-
sion can actually sidestep the arguments of Kinnen and Rubia (1981)
against the origin of Centauros in high energy cosmic ray collisions.
The latter authors have concluded so by noting that the kinematics of the
Cenaturo event demand y = 104 and Mfireball = 200 GeV. Assuming further(as they did) that all the primary energy goes into making the rest mass
energy of the fireball (i.e. y, =Y_M)' they derived from the latter
figures a primary energy E_ = y_.. _']' • _. = I017 eV. The flux of
cosmic rays at these energies is_ch _'(_D1aC_v_to account for the observed
Centauro rate. Eq. (6) however shows that if the bubble is created in
the CM frame with a Lorentz factor f = i0 then y, = 104 implies y 109
and hence a primary energy E. = 1015 which provides sufficient C_ux to
account for the observed rate, I
3. Discussion - Conclusions. The next question one is called to answer
_'s the nature of these "fireballs". (See Kazanas et ai.1984). We
consider the possibility of the SU(2)xU(1) vacuum as a means for
producing these "fireballs". At the restoration of the symmetry there is
a contribution to the energy density from the SU(2)xU(1) vacuum. The
total energy density, _, is then
= An4/3 + p
The first term is the energy density due to the quarks participating in
the collision (assumed to be cold) and the second term the energy density
of the vacuum. The pressure of the mixture can then be calculated using
the thermodynamic relation
dc 1 An4/3_
P = n_-_--c =-_ p .
One can now observe that for An4/3 : p (i.e. close to the phase transi-
tion point) the pressure of the mixture goes to zero and the medium
becomes unstable to bubble formation. It is assumed that at T = T the
two phases with <@> : 0 and <@>_ 0 coexist since the height o_ the
barrier between them is smaller than the thermal energy for T > T (Sher
and Flores 1983). Neglecting surface effects, the bubbles ar_ .nc pres-
sure equilibrium between the positive particle pressure and the negative
vacuum tension. The bubbles should therefore decay primarily into Higgs
particles. It has been suggested (Willey 1984) that the particle _(2.2)
_bs.erved in the decay J/_.y+_(2.2) might be the Higgs boson. Such an
identification would indeed fit the signatures of the Centauros. A_
100 GeV bubble/would decay into ~ 50 Higgs and subsequently into ~
100 KI_(C(2.2).I_Kdominantly). These K's would have Pt ~ 1 GeV and
would explain the absence of _°'s. Also only explosions close to the
detector would classify as Cenaturos since for dL>300 m the K's would
have a chance to decay into _°'s, and then into photons.
4. References
i. Bjorken, J_ D. and McLerran, L. D. Phys. Rev. D20 (1979), 2353.
2. Kazanas, D. et al. 1984, Phys. Let. 142 23.
3. Kinnunen, R. and Rubbia, C. 1981, Pr_ 17th ICRC, Paris, 11, 112.
4. Lattes, C. et al. 1973, Proc. 13th ICRC, Denver, 3, 2227; T,, 2671.
5. Sher, M. and Flores, R., Anny. Phys. 148 (1983), 9--5.
6. Willey, R. S., Phys. Rev. Lett. 52 (1984), 585.


SU(2) x U(1) vacuum and the Centauro events

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4w
(NASA-Td-86082)
	 SU % 2) x U (1) VACUUM AND ZbE
	 N85-17926
	
i
CENTAO@U EVENZS (6A5A) 15 p EC A02/MF A01
CSCL 03B
U,. Clas
G3/93 17334
1
Technical Memorandum 86082
SU(2) X U(1) VACUUM AND THE
CENTAURO EVENTS
D. Kazanas
V. K. Balasubrahmanyan
R. E. Streitmatter
.4
e
APRIL 1984
S ^'
National Aeronautics and
Space Administration
Goddard Space Flight Centee
Greenbelt, Maryland 20771
O
SUM x U(1) VACUUM AND THE (,CNTAURO EVENTS
D. Kazanas 1,2 , V. K. Balasubrahmanyan2
and
R, E. Strtitmatter2
1 Dept. of Physics and Astronomy, U. of Maryland, College Park, MD. 20742
2NASA/Goddard Space Flight Center, Code 661, Greenbelt, MD. 20711.
J
FT.. ^_ L ^`
2
ABSTRACT
We propose that the "fireballs" invoked to explain the Centauro [11
events are bubbles of a metastable superdense state of nuclear matter, created
.n hiyh energy (E — 10 15 eV) cosmic ray collisions at the top of the
atmosphere. If these bubbles are created with a Lorentz factor Y = 10 at
their CM frame, the objections against the origin of these events in cosmic
ray interactions are overcome. Assuming further, that the Centauro events are
due to the explosive decay of these metastable "bubbles", a relatiolship
between their lifetime, T , and the threshold energy for bubble formation,
E th , is derived. The minimum lifetime consistent with such an interpretation
is T — 10 -8 sec, while the E th appears to be insensitive to the value of T
and always close to E th — 10 15 eV. Finally it is speculated that if the
available CM energy is thermalized in such collisions, these bubbles might be
manifestations of excitations of the SU(2) x U(1) false vacuum. The absence
of n o 's in the Centauro events is then explained by the decay modes of these
excitations.
J
3Introduction
The Centauro, [1] mini-Centauro and other "unusual" cosmic ray events
(Chiron, Geminion) are high energy (= 10 15±1 eV) cosmic ray events detected in
nuclear emulsion chambers at high altitudes (> 4000 m) with characteristics
which defy explanation in terms of "standard" high energy cosmic ray
collisions and subsequent cascading of the produced particles [2]. We
presently focus our attention on the so called Centauro events which have been
the subject of controversy over many years. The characteristics which set
these events apart from the typical events expected at these
energies (= 10 15 eV) are the following:
a. They are observed deep in the atmosphere (~ 500 g cm -? ), only a few
hundred meters above tnP emulsion chamber detector.
b. They have very high mult1,,licity.
c. They have very large mean transverse momentiim, < p t >, 3-5 times larger
than that of a typical nuclear fragmentation interaction.
d. There is a deficiency of neutral pion production.
It was immediately realized that direct nuclear collisions failed to
account for any of the above features, especially for the observed rate,
R = 10 -2 m-2 sr -l yr -1 , since the probabilty of penetration of a strongly
interactiny particle to such depths is negligible. 	 It was also pointed out
though, that most of the above features (multiplicity, <P t >) as well as toose
of other "unusual" events [3], could he accounted for in terms of the
explosive decay of an unknown state of w.atter. Rjorken and McLerran [4] for
instance, postulate a new metastable form of quark matter, introducing a new
component in the cosmic ray spectrum, wh i le Kinnunen ana Rubbia [51 argue that
these events cannot be due to high energy cosmic ray interacti,,ns, thus in
effect ayreeing with the previous authors. 	 In the present note we accept the
Im-9
4
interpretation of the Centauro events as the explosive decays of an unknown
yet high energy particle deep in the atmosphere. However, contrary to the
previous treatments, we relate the Centauro flux to the flux of high energy
cosmic ray particles at the top of the atmosphere, thus avoiding the
;rtroduction of a new, unknown component in the primary cosmic ray spectrum.
Tien, the requirement that Centauros are due to the Explosive decay of a
bubble of a metastable superdense nuclear matter, produced in a high energy
collision on toe top of the atmosphere, leads to a relation between the
formation of such a metastable state and to its lifetime. This is done in the
next section.
The Centauro Event Rate
In relating the Centauro rate to that of high energy cosmic ray
interactions, we shall assume that a large fraction of high energy cosmic rays
have interacted within 5U g cm- 2
 frcn
	
top of the atmosphe r e, which sets
the inte r .^,tion height to about 21 km. Given that the Mt. Chacaltaya detector
is at a depth — 500 g cm- 2
 or a height of — 6 km, the bubbles of metastahle
matter wiii have to traverse a distance of about 15 km before they decay. We
further assume that any decay at a distanc., dL > 100 m from the detector does
not classify as a Centauro event, because the ensuing cascade will not have
the characteristics of a Centauro (i.e. closeness to the detector, few
IT 01
	
Then if To is the lifetime of the bubble and YL its Lorentz factor in
the laboratory frame, the decay rate of bubbles as a function of time after
the interaction will be
N(t) = N T e -t/YL T 0	 (1)
or in terms of the distance d from the high energy interaction point,
N(d) = N T e -d/cY LT 0	 (2)
V
5Wh,. •e NT is the rate of bubble production at the top of the atmosphere. Then
the differential rate with respect to the pathlength dl within which decays
are identifiable as Centauro events is
dN(d) _	 1	
N(d)
-I — C YL TD
and the Centauro event detection rate should be
R =	
d l	 N e-d /cYLTo
cY L To T
	 (3)
Solving this relation for the rate of events at the top of the atmosphere, NT,
one obtains
N T = R YL` 0  ed /cYLTo	 (4)
Since we expect the formation of bubbles to have a threshold energy E i , NT
should be the integrated cosmic ray flux at the top of the atmosphere with E >
E i or
NT = n K E-1.7 = n 1.1 104 E-1.7 m-2 Sr -2 S -1	 (5)
with E i
 measured in GeV. The factor n denotes the fraction of these events
that produce bubbles of metastable nuclear matter, which we will presently
assume to be of the order of 1 (n = 1). The only thing now needed is a
relation between E i and YL so that we obtain a relation between Ei and To. if
Mb
 is the mass (rest energy) of the bubble and E*b its CM energy then its
Lorentz factor in the interaction CM frame will he
f = E*b/mb
6Hence the Lorentz factor of the CM will be YCM = (Em—
P
Consequently the Lorentz factor of the bubble in the laboratory frame, YL,
will be
Y	 EL = M lab = YCM f + (YCM-1)1/2
	 (f 2
-1) 1/2 cose* =f ( F^ ) 1/2	 (6)
b	 p
Substituting equations (5) and k'6) into equation (4) and solving for E i we
obtain the transcendental equation
Ei = [7 
-T 
(x)1/2 f T
o
 Pxp (d/c (	 f To))	 ( 7)x ) 1/2	 -0.59 
where R = 10- 2 m- 2 sr -l yr -1 is the Centauro event rate, dl = 10 4 cm, d = 15 km
= 1.5 x 106
 cm, K is defined by equation (5), and m  has been taken as 1
GeV. Substituting the numerical values equation (7) reads
E i = [n 5.68 x 108 E. 1/2 f To exp (7.07 10 5/E i
112
f To ). -0.59 =-F (Ei, TO)
(7a)
Equation (7a) can be solved graphically by plotting the curves y = F i and y =
F(E i , T o ). The results are shown in figure 1 where the familes of curvPs
F(E i , To ) are shown as a function of E i with fTo as a parameter. ThP study of
these curves points out two major features: 	 (i) For sufficiently small
values of the parameter fT o (<10- 8 ) no solution to equation (7a) exists. This
means that for sufficiently small bubble lifetimes (fr o <10-8 ) not enough of
them will survive deep enough in the atmosphere to account for the observed
Centauro flux, (ii) For fTo >10-8 there are always two solutions to equation
(7a) since the curve y = E i intersects the curve y = F(Ei, ro) at two
points. It is interesting to note that of these two solutions the highest
i
7ones are always close to an energy E i = 106 GeV for a wide range of values of
the naramter fr o , (10
-6 -10-8 ), which corresponds to a CM energy of = 1 TeV.
The lower energy solution however shifts quickly to much lower energies (CM
energies < 100 GeV for fT o > 10-7
 sec.). Center of mass energies much smaller
than 100 GeV however may have to be excluded on the basis of lack of such
events in accelerator experiments. One should also note the dependence on the
assumption n = 1.
	 If n << 1 the whole figure would shift downward thus
indicating longer lifetimes and lower threshold energies.
The assumption that the bubbles of the superdense metastable nuclear
state are produced with a certain kinetic energy at the CM of the collision
can actually sidestep the arguments of ref. [51 against the origin of
Centauros in high en^rgy cosmic ray collisions. The latter authors have
reached that conclusion by noting that the kinematics of the Cenaturo event
demand Y = 10 4 and M fireball = 200 GeV. Assuming further (as they dirt) that
all the primary energy goes into making the rest mass energy of the
fireball (i.e. t  = YCM ), they derived from the latter figures a primary
eneryy Ei
	 YCM Mfireball = 10 17 eV. The flux of cosmic rays at these
energies is much too low to account for the observed Centauro rate. Eq. (6)
however shows that if the bubble is created in the CM frame with a Lorentz
factor f = 10 then y  = 10 4 implies YCM = 10 3 and hence a primary energy
E  = 10 15
 eV, which provides sufficient flux to account for the observed
rate.
Discussion - Conclusions
Motivated by the extraordinary properties of the Centauro events we have
reexamined the "fireball" hypothesis. In contrast to the previous treatments,
we have tried to avoid the introduction of a new component in the primary
D.
8cosmic W ays, but we have instead examined the possiblity of producing the
metastable high density [hase of ,natter needed to account for the "fireballs"
in high energy cosmic ray collisions on the top of the atmosphere.
Establishing such a connection leads to the relation of fig 1 between the
threshold energy for the production of the metastahle bubhles and their
lifetimes.
The next question one is called to answer is the nature of these
"fireballs". A clue to this question comes from the large P t observed in
these events. The value of P t
 observed indicates, as pointed oot [ref. 41, a
superdense state of matter with mean particle separation, k, 3-5 times smaller
than that of quarks in a nucleon. Since the corresponding energy density is
expected to be E — n4/3 _ (1/Z) 4 , (n is the quark number density) it would
correspond to energy densities — 80-600 times those of nuclear matter. Hence
the matter is expected to be in the quark-gluon phase. Unfortunately the
phase transition from the quark to nuclear matter is considered to take place
at much lower energy densities, a few GeV fm- 3 , and therefore does not appear
to account for the observed magnitude of P t
. Also the decay of such quark-
gluon balls should produce 7"s contrary to observation.
In search of another scale at higher energy densities, the intriguing
possibility of the SU(2) x U(1) i U(1) symmetry breaking scale has heen
considered. If the symmetry is restored there is a contrihution to the energy
density from the SU(2 1 x U(1) vacuum. The total energy density, E, is then
E= An4/3+p
The first term is the energy density due to the quarks participating in the
collision (assumed to be cold) and the second term the energy density of the
J
PV,r
R
9	 ;1
vacuum. The pressure of the mixture can then be calculated using the
thermodynamic relation
P= n dL- e= i An" /3 - p.
One can now observe that for An 4/3 = o (i.e. close to the phase transition
point) the pressure of the mixture goes to zero and the medium becomes
unstable to bubble formation. It is assumed that at T = T c
 the two phases
with <o = 0 and <0> * 0 coexist since the height of the harrier between them
is smaller than the thermal energy for T > T c
 [6]. Neglecting surface
effects, the bubbles are in pressure equilibrium between the positive particle
p ressure and the negative vacuum tEnsion. These bubbles would presumably
survive as long as the false vacuum state i^ prese ,-ved and does not decay to
its minimum energy state (true vacuum). From the formal point of view the
SU(2) x U(1) vacuum acts in a similar way as the constant bag energy density
of QCD (which presumably is due to the SI1(3) vacuum; see ref. 7), to form
bound metastable objects. The difference is that the SU(2) x II(1) vacuum is
metastable and these objects will decay with the decay of the false vacuum.
However for this situation to occur the energy density achieved in the
collision should be of the order of that required to restore the Sll(2) x, 11(1)
i
symmetry. This is roughly the energy density corresponding to black hody	 i
radiation of temperature equal to the critical temperature for SU(2) x U(1)
breaking. This is expected to be T — mH , where m 	 is the mass of the Higgs
boson. This mass cannot be determined from the theory and it is currently
unknown. Taking however at face value the observed P t
 for the Centauro
events, and assuming as a working hypothesis, that is due to the decay of
metastable vacuum into Higgs particles which further decay into Kaons, one is
- *0
10
lead to m  - 2pt
 or 2-3 GeV. It is interesting to note that this value for WH
naturally accounts for the large observed multiplicity, since an ohjec^
similar to that considered to account for the Centauros with M 	 100 GeV will
,22cay into - 50 Higgs particles which will further decay into	 100 KK (see
further discussion). One should mention at this point that there is a lower
limit to the mass of the Higgs boson within the minimal (one Higgs doublet)
standard model, of the order of mH > 10 GeV [H]. However models with extended
Higgs sector [9], [10] can actually circumvent this limit. 	 It has actually
been suggested [10] that the particle x(2.2) observed in the decay
J/y +Y+x(2.2) might indeed be the long sought Higgs hoson. 	 It is encouraging
that this value is consistent with the observed value of P t as argued ParliPr.
The most serious problem concerning such an ;nterpretation of the
Centauro events is the achievement of energy densities > 100 times that of
ordinary nucleons (or 30-60 GeV rm-3 ), needed for the restoration of SU(2) x
U(1) symmetry, in view of the aryuments put forward in ref. [I'.]. These
authors have argued that at high energies the nuclei become transparent to
each other thus limiting the maximum energy density achieved in a collision.
Since, no definite answer to this question can presentl y he given and since
the required energy density is within an order of magnitude of the ones
presently considered achievable we consider that such a possihility exists.
Such a point of view is actually supported by the evidence for apparent
scaling violation both in high energy cosmic ray interactions x121 and
in pp collider experiments [13].
	
It is interesting to note that the energy 	 at
which evidence for such violations occurs (as quoted by the above authors) is
10 15 eV, in good agreement with the threshold energy for Centauro
productions as derived graphically in fig. 1.
One can of -ourse always argue that such structures have very long life
0
11
times and were created in the early universe [4], since at sufficiently early
times the temperatures were high enough for the SU(2) x U(1) symmetry to be
restored. Unfortunately this scheme, although it mry account satisfactorily
for the production cf such objects, requires the introduction of several other
parameters (their life times, spectrum, number density etc.) in an art hoc
manner. While such a possibility cannot he dismissed it appears to he at
least for the present, intractable.
Finally there is one more issue to be addressed, namely the apparent
absence or deficiency of neutral pions or photons in these events, which
should be explained in terms of the decay modes of the form of matter
considered to comprise the fireballs.
	
If our hypothesis is correct and the
"fireballs" are due to false vacuum excitations, one would expect them to
decay into Higgs particles, since the Higgs field is the agent responsible for
the breaking of the symmetry. The Higgs should then suhsequently decay,
preferably into heavy quarks (Nussinov, private communication) since the
coupling of Higgs to fermions is proportional to the square of the fermion
mass.	 It is at this point that the identification of the x(2.2) meson with
the Higgs boson [10] provides evidence in support of our hypothesis and
ayreement with observation. 	 If such an identificat i on can indeed he made one
would expect the Higgs bosons to decay primarily into the heaviest quarks
lighter than `he Higgs i.e. into Kaons (which is actually ohserved i^	 ^e
(2.).) decay).	 The Kaons have sufficiently long life times (even for
K s , T - Ii) -10 sec) that with a Lorentz factor Y = 10 4 (as observed for the
Centauro) they would have to traverse -- 300 m before they would decay into
pions. So in this scenario the absence of pions would be accounted for by the
closeness of the fireball to the detector (— 50 m). 	 It is interesting to notf^
that other similar events (mini-Centauros) which apparently release the
1?
fireball energy a few hundred meters from the detector show a deficiency
rather than absence of pions, potentially accounted for by the same ar3ument.
We would li!;e to acknowledge discussions with Tom Gaisser, S. Nussinov, Jon
Orines and Quaisar Shafi.
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[3] N. J.	 Capdevielle	 et	 al.,	 Proc.	 17th	 I.C.R. , .,	 Paris,	 (1 q ,1),	 11, 11?,
[4] J. 0.	 Bjcrken and	 L.	 D.	 McLerran,	 Phys.	 Rev.	 020	 (19 7 9),	 2353.
[5] R. Kinnunen	 and	 C.	 Rubhia,	 Proc.	 11th	 I.C.R.C.,	 Paris,	 (1981),	 11, 11?.
[6] M. Sher	 and	 R.	 A.	 Flcres,	 Anny.	 Phys.	 148	 (1083),	 91,
[7] G. Baym,	 in	 "Quark	 Matter	 Formation	 in	 Heavy	 Ion	 Collisions",	 M.	 Jacoh
and H.	 Satz	 editors,	 World	 Scientific,	 (1982).
[ 3 ']	 A. D. Linde, JETP Lett. 23 (1916), 64.
S. Weinberg, Phys. Rev, Lett, 36 (1976), 294.
[9]	 F. Wilczek, Phys. Rev. Lett. 39 (1977) 1304.
[1U]	 R. S. Willey, Phys. Rev. Lett. 52 (1984), 585.
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SU(2) x U(1) vacuum and the Centauro events

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