alrm ingles
TRANSCRIPT
Rare top decays in Extended
Models Ricardo Gaitán Centro de Investigaciones Teóricas, Facultad de Estudios Superiores - Cuautitlán,
Universidad Nacional Autónoma de México, (FESC-UNAM).
Omar G. MirandaDepartamento de Física, Centro de Investigación y de Estudios Avanzados del
IPN, (CINVESTAV).
Luis G. Cabral-RosettiDepartamento de Posgrado, Centro Interdisciplinario de Investigación y Docencia
en Educación Técnica, (CIIDET).
Phys. Rev. D 72, 034018 (2005)
X Mexican Workshop on Particles and FieldMorelia Mich., November 7-12, 2005.
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OVERVIEW
1) Introduction
2) Alternative left-right symmetric Model (ALRM)
3) Top and Higgs decays in the ALRM a) Constraining the top-charm mixing angle b) The decay: t → H° + c c) The decay: t → H° +
4) Results and Conclusions
c̄
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1) Introduction
The top quark was regarded as an essential ingredient of the Standard Model (SM) of particle physics. Its existence, and many of its properties, are determined by the following requirements: theoretical consistency of the Standard Model gauge theory (anomaly cancellations), consistency of b quark measurements with SM predictions, and consistency of precisions measurements with the SM.
The top quark mass, which is measured at CDF and D0 to be approach 174 GEV´s,is not predicted in the SM, but is restricted by precision electroweak measurements. The fact that the top quark is much heavier than the other quarks gives it a special role in electroweak symmetry breaking.
Top quark properties:
2| |
3temQ e
Weak isospin partner of b quark 3
1
2tT
Color triplet
Spin- 1
2
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1) Introduction
The mixings will affect the couplings to the neutral current (NC) and the charged current (CC) of the known neutral states, and then could be restricted by the precision tests of the SM.
ORDINARY AND EXOTIC FERMIONS
Different extensions of the STANDAR MODEL (SM), such as the Models withLeft-Right Symmetry, SO(10) and E(6), predicts the existence of new fermions with exotic SU(2) X U(1) assignments.In addition to direct production, these new fermions can manifest themselves through their mixing with the known quarks and leptons.
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1) Introduction
Standard Model
, ,
, ,
e
L L L
L L L
e
u c t
d s b
doublets in SU(2) singlets in SU(2)
, , ,
, , ,
, ,
R R R
R R R
R R R
e
u c t
d s b
There are several possibilities for new fermions. The sequential fermions are repetitions of the known fermions, with canonical (L-doublets , R-singlets) SU(2) X U(1) assignments. The mirror fermions are L-handed singlets and R-handed doublets of SU(2). The vector doublets concern to new quarks o leptons where the L and R-handed components are SU(2) doublets. The vector singlets are new particles for which L and R are SU(2) singlets . Also, there are SU(2)-singlet Weyl. Finally, one can introduce exotic electric charge or color assignments.
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1) Introduction
MIXING WEAK-HEAVY
Vectors for the ordinary weak eigenstates and exotic, left and right are grouped in the column vector:
00
0
( )
ord
ex L R
n
Vectors for the light mass eigenstates (standard) and heavy are grouped in the column vector:
( )
l
h L R
n
The relation between weak eigenstates and mass eigenstates will be given through
0( ) ( )L R L Rn Un
with( )
( )
L R
L R
A EU
F G
, U U I
From the unitarity of U is obtained:
where I is the identity matrix, i.e.
A A F F A A E E I 0
0
II
I
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1) Introduction
NEUTRAL INTERACTIONS WITH FLAVOUR CHANGE OF THE TOP
The next generation of high energies colliders, planned or in construction, will probe the Standard Model (SM) with high precision, and they will explore higher energies in the new physic research.
The new Physics could be manifest in two ways: through direct signals including the production of new particles or departure of the SM predictions for known particles.
The quark top plays an important role in the search of departures of the SM predictions for two reasons:
1) Because their great mass, the radiative corrections that include new particles, frequently are more important than for the light fermions. 2) Their great mass (approximately 178 GeV’s) suggest that it may be plays
an special role in the electroweak symmetry breaking.
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Quarks top could be copiously produced in LHC and in colliders e+e- of high energy such as TESLA. With these big probes, we will to have more precise measures of their coupling to probe the SM.
Is very important the study of the flavor changing neutral currents with (FCNF) including the quark top. The quark top decays induced by FCNC are extremely rare events in the SM.
In the ME,
13( ), ( ), ( ) 10BR t c BR t c Z BR c H 13( ) 10BR H t c
Considering physics beyond the SM, there are new possibilities that could change radically the pessimist prospectus for the FCNC decays that include a Higgs boson and a quark top
Two Higgs Doublets Model (2HDM)Minimal Supersymmetric Standard Model (MSSM)
Example:
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2) Alternative left-right symmetric Model (ALRM)
LBRL USUSU )1()2()2(
00
0
0000
0
00
0
0
000
0
00
ˆ,ˆ,ˆˆˆ;,,
ˆ,ˆ
ˆˆ;,
iLiL
Ri
iiRiRiR
Li
iiL
iL
Ri
iiRiR
Li
iiL
dud
uQdu
d
uQ
ee
lee
l
vv ˆ
0
2
1ˆ;0
2
1
The gauge group of ALRM is:
cos)ˆ(sin)(2ˆ
sin)ˆ(cos)(200
00
veveH
veveH
Fermionic sector:
The Higgs fields:
where denotes the neutral Higgs mixing angle.
The neutral and massive Higgs bosons are:
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2) Alternative left-right symmetric Model (ALRM)
Higgs boson and quarks interaction
matrix.Paulithe
with,ˆ~̂and~are
~̂~fieldsconjugateThematrices.unknown
areand,ˆ,and3,2,1,where
..ˆˆˆ~̂ˆˆ
ˆˆˆˆ~
2*
2*
2
)()()(
000000
000000
ii
ji
chuudduQ
dQuQdQ
udij
udij
udij
jRiLuijjRiL
dijjLiR
uij
jLiRdijjRiL
uijjRiL
dij
qY
L
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2) Alternative left-right symmetric Model (ALRM)
..)cosˆsin(22
ˆ
)sinˆcos(22
ˆ
chHHFFM
mg
HHM
mAA
g
RRR
W
fL
RW
fLLL
fY
L
The tree-level interactions of neutral Higgs bosons H and H with the lights fermions are given by:^
level. at tree FCNC havecan we
matrices, theofy nounitarit the to thanks that,seecan weequations, last two Fron the
ly.respective,)1(and,)2(,)2(ofgeneratorstheareand,ˆ,where
,ˆ2
´,ˆˆ,
33
33,
a
LBRLaa
aaa
aaaRLa
a
A
USUSU
A
Z
Z
ggg
YTT
UY
TTU c.n.- L
The neutral current in terms of the mass eigenstates, including the contributions of the neutral gauge boson mixing, can be written as follows :
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3a) Constraining the top-charm mixing angle
53.032
32323232
32
2
32
2
,
)(;)(
41
41
where,)(
RRR
LLL
RLAV
AVctZ
AAAA
sr
cs
r
scg
tZggccse
W
W
W
W
WW
L
1.032
From BR( t → Z + c) and comparing with the experimental limit, we obtain that
FC coupling of Z to top-charm quarks
From
We obtain that:
)1)(1( 2233
2
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3b) The decay: t → H° + c
2/12222
22222
320
216
cos)(
cHtcHt
Hctt
F
mMmmMm
Mmmm
GcHt
LW
t PMmg
cos2
32
)()(
)(0
0
WbtcHt
cHtBR
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3b) The decay: t → H° + c
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3c) The decay: H°→ t +
2/12222
2223
22320
28
cos3)(
tcHctH
ctHH
tF
mmMmmM
mmMM
mGctH
c̄
quarks.for3and
leptonsfor1,)/(where
4124
cos)(
2
2/3222
0
f
fHff
fffHfF
f
C
CMm
MmGCffH
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3c) The decay: H°→ t +
2
2/123
0
)/(with
4128
cos)(
HWW
WHF
MM
MGWWH
c̄
22
2
2/1
4
22430
/and
)/(with
1241
41216
cos)(
crstrsccX
MM
M
XMMGZZH
WWWWW
HZf
ZZ
ZZ
WHF
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3c) The decay: H°→ t + c̄
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4) Results and Conclusions
32
)( cHtBR 410
1) The model allows relatively big values of
2) The could be of order of , which is at the reach of LHC.
3) The may reach a value of order and can also be an useful channel to look for signals of new physics in LHC.
310
)( ctHBR