Lecture 8
description
Transcript of Lecture 8
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Lecture 8
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OverviewFinal lecture today! Can cover the following topics today: Sfermion, chargino and neutralino masses
Fine Tuning What this really means, how we may quantify it. How LHC squark, gluino and Higgs searches affect this
Changing universality assumptions Relaxing some constraints Using different breaking scheme inspired constraints
Non-minimal Supersymmetry Extend the chiral superfield contentExtend the gauge structure
Can give overview of all or focus on one or two?
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MSSM Chiral Superfield Content
Left handed quark chiral superfields
Note: left handed fermions are described by chiral superfields, right handed fermions by anti-chiral superfields. Superpotential is a function of chiral superfields only so we include right handed fermions by taking the conjugate, which transforms as a left handed superfield!
Conjugate of right handed quark
superfields
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MSSM Lagragngian densitySuperpotential
With the gauge structure, superfield content and Superpotential now specified we can construct the MSSM Lagrangian.
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EWSB conditions
VH = (m2H d + j¹ j2)jH 0
d j2 + (m2H u + j¹ j2)jH 0
uj2 ¡ B¹ (H 0uH 0
d + h.c.)+1
8(g2 + g02) ¡jH 0d j2 ¡ jH 0
u j2¢2
For successful EWSB:(m2
H d + m2H u + 2j¹ j2) ¸ 2B¹
(m2H d + j¹ j2)(m2
H u + j¹ j2) · (B¹ )2
With:
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Higgs Masses
Goldstone bosons
CP-even Higgs bosons
Charged Higgs boson
CP-odd Higgs boson
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Sfermion masses
Softmass: (m2)ji Ái Á¤
j + 16ai j kÁi Áj Ák
m2~f L
~f L ~f L + m2~f R
~f R ~f R + Amf ~f L ~f R
(mF L )i j ~f iL ~f ¤ j
L + yf A f Hu=d ~f iL ~f ¤ j
RFlavour diagonal postulate
Hu=d ! vu=d
F-terms
FH u = ¹ Hd + yi ju ~ui ~Qj FH d = ¹ Hu + yi j
d~di ~Qj + yi j
e ~ei ~L j
jFH u j2 yu¹ Hd~u ~Q jFH d j2 yd¹ Hu~d~Q + ye¹ Hu~e~L
jFf R j2 + jF f L j2
D-terms
¢ ~f L = 14(T3 ~f L g2 ¡ Y~f L g02)(v2
d ¡ v2u)
¢ ~f R = ¡ 14Y~f L g02(v2
d ¡ v2u)
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Sfermion masses
L 3r dgen~f ¡ mass = ¡ (et¤
L et¤R ) m2
etµ etL
etR
¶¡ ¡ eb¤
L et¤R
¢m2eb
µ ebLebR
¶¡ ( e¿¤
L e¿¤R ) m2
e¿µ e¿L
e¿R
¶
where
m2et =
µ m2Q3 + m2
t + ¢ ~uL mt(A¤t ¡ ¹ cot ¯)
mt(At ¡ ¹ ¤ cot ¯) m2u3 + m2
t + ¢ ~uR
¶:
m2eb =
µ m2Q3 + m2
b + ¢ ~dL mb(A¤b ¡ ¹ tan¯)
mb(Ab ¡ ¹ ¤ tan¯) m2d3
+ m2b + ¢ ~dR
¶:
m2e¿ =
µ m2L 3 + m2
¿ + ¢ ~eL m¿ (A¤¿ ¡ ¹ tan¯)
m¿ (A¿ ¡ ¹ ¤ tan¯) m2e3 + m2
¿ + ¢ ~eR
¶:
Home exercise: find all the mistakes on the previous slide, then write in matrix form below and diagonalise.
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Chargino and Neutralino masses
a) Find all the mass terms involving gauginos and Higgsinos in the MSSM,including soft SUSY breaking terms and any superpotential mass terms.
M1 ~B ~B + M2 ~Wa ~WaSoft masses:
Superpotential: ¹ ~Hu ~Hd
Kahler potential:
VEVs
(Home exercise)
Hints:
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Chargino and Neutralino masses
b) Show that the mass terms for the charged states may be written as,
¡ 12[~g+ T X T ~g¡ + ~g¡ T X ~g+]+ h:c: = ¡ 1
2µ ~g+
~g¡
¶T µ 0 X T
X 0¶ µ ~g+
~g¡
¶+ h:c:
where the states ~g+ and ~g¡ are de ned as
~g+ =µ ~W+
~H +u
¶~g¡ =
µ ~W ¡~H ¡
d
¶
and
X =µ M2
p 2sin¯MWp 2cos¯MW ¹¶
with theMW = g2
4 v2 being themass of the W boson.Since X T 6= X we must perform a biunitary transformation to diagonalise
it.
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Chargino and Neutralino masses
c) Convinceyourself that onecan diagonalise this using unitary matrices U,V, so that
U¤X V ¡ 1 =Ã
m~§1
00 m~§
2
!with ~Â+ = V~g+ and ~¡ = U~g¡
the check that
VX yX V ¡ 1 = U¤X X yUT =Ã m2
~§1
00 m2
~§2
!
and use this to ¯nd expressions for the mass eigenstates m~§1
and m~§2
.
d) Convinceyourself that thesearethedoubly degenerateeigenvalues of the4x4 mass matrix, M y
~ÂM ~Â, where,
M ~Â =µ 0 X T
X 0¶
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Chargino and Neutralino masses
e) In a similar fashion write the mass terms for the neutral states as
Lneutralino mass = ¡ 12Ã0T M ~N Ã0 + c:c (1)
where Ã0T = ( ~B; ~W0; ~H 0d; ~H 0
u), giving the matrix M ~N .
M eN =
0B@
M1 0 ¡ g0vd=2 g0vu=20 M2 gvd=2 ¡ gvu=2
¡ g0vd=2 gvd=2 0 ¡ ¹g0vu=2 ¡ gvu=2 ¡ ¹ 0
1CA :
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parameter space volume restricted by,
Parameter space point,
Tuning:
`` ``
Compare dimensionless variations in: ALL parameters vs ALL observables
Our ApproachPA & D.J.Millier PRD 76, 075010 (2007)
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parameter space volume restricted by,
Parameter space point,
Tuning:
`` ``
Compare dimensionless variations in: parameters vs observables
Our ApproachPA & D.J.Millier PRD 76, 075010 (2007)
Probability of random point from lying in :
But remember any parameter space point is incredibly unlikely if all equally likely (flat prior)! Fine tuning is when a special qualitative feature ( ) is far less likely that other typical case ( )
mh = O(10¡ 17MP l)mh = O(MP lanck)
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Any G << F
parameter space volume restricted by,
Parameter space point,
Tuning:
`` ``
Compare dimensionless variations in: parameters vs observables
Our ApproachPA & D.J.Millier PRD 76, 075010 (2007)
Probability of random point from lying in :
But what if :
) 4 large for all points (or all values of O)
Global sensitivity (Anderson & Castano 1995)
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Any G << F
parameter space volume restricted by,
Parameter space point,
Tuning:
`` ``
Compare dimensionless variations in: parameters vs observables
Our ApproachPA & D.J.Millier PRD 76, 075010 (2007)
Probability of random point from lying in :
But what if :
) 4 large for all points (or all values of O)
Rescale to our expectation for
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Regardless of measure details, fine tuning is increased when searches increase mass limits on squarks and gluinos:
M 2Z = 2(¡ j¹ j2
+0:076m20
+1:97M 21=2
+0:1A20
+0:38A0M1=2)Search pushes up. M1=2
Larger cancellation required!
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What about the Higgs?
Heavy stops ) Large soft masses
and large one loop corrections
M 2Z = 2(¡ j¹ j2 + 0:076m2
0 + 1:97M 21=2 + 0:1A2
0 + 0:38A0M1=2)
+@
@vd(¢ V) ¡ tan¯ @
@vu(¢ V)
vd(tan2 ¯ ¡ 1)
A relatively heavy Higgs requires heavy stops
Break cMSSM link between stop masses and light squarks and evade fine tuning
LEP bound ) tuning » 10¡ 100mh = 126 GeV Tuning?Tentative LHC Higgs signal
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Fine Tuning Summary
Most important consideration at the LHC (by far) is what do we seec Higgs? Beyond the standard model (BSM) signal?
If BSM signal is observed initially all efforts on understanding new physics. Eventually will know if new physics solves Hierachy Problem Residual tuning may also be a hint about highscale physics
If no SUSY signal? Where does that leave us? Subjective question, depends on tuning measure, but also prejudice Conventional wisdom: no observation ) SUSY is fine tuned! Motivation for low energy SUSY weakened (doesn’t remove fine tuning).
No BSM signal at all Hierarchy Problem motivated BSM models have tuning too. Nature is fine tuned? SM true up to Planck scale? Or we need some great new idea
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Beyond the CMSSM(Relaxing high scale constraints)
Non-universal Higgs MSSM (NUHM)
Motivated since Higgs bosons do not fit into the same SU(5) or SO(10) GUT multiplets:
10
5*
+
1
+16
105
5*
Color triplets+
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Beyond the CMSSM(Relaxing high scale constraints)
Non-universal Higgs MSSM (NUHM)
Impact: Higgs masses not linked to other scalar masses so strongly easier to fit EWSB constraints and other observables
Motivated since Higgs bosons do not fit into the same SU(5) or SO(10) GUT multiplets:
Very mild modification to the CMSSM
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Beyond the CMSSM(Relaxing high scale constraints)
Non-universal Gaugino masses
For universal gauginos we have a (one loop) relation:
Testable predictions for gaugino universality!
Breaks ratio get different gaugino mass patterns:
One can also ignore the universality more parameters to consider the model with less prejudice, e.g. pMSSM
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In gauge mediated symmetry breaking the SUSY breaking is transmitted from the hidden sector via SM gauge interactions of heavy messenger fields.
Chiral Messenger fields couple to Hidden sector SUSY breaking in messenger spectrum
SM Gauge interactions couple them to visible sectorLoops from gauge interactions with virtual messengers flavour diagonal soft masses.
Non-universal soft gaugino masses since they depend on gauge interactions!
Soft mass relations imposed at messenger scale
Gauge Mediation
More details and a more general definition given in Steve Abel’s lectures
Loop diagram:
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Minimal Gauge Mediated SUSY Breaking (mGMSB)
Messenger fields form Complete SU(5) representations
From EWSB as in CMSSM
Number of SU(5) multiplets
Messenger scale
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Beyond the MSSMNon-minimal Supersymmetry
The fundamental motivations for Supersymmetry are:- The hierarchy problem (fine tuning)- Gauge Coupling Unification- Dark matter
None of these require Supersymmetry to be realised in a minimal form.
MSSM is not the only model we can consider!
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The MSSM superpotential is written down before EWSB or SUSY breaking:
The problem
What mass should we use?
The natural choices would be 0 or MPlanck (or MGUT)
) it should know nothing about the EW scale.
Phenomenological Constraints ) ¹ ¼ 0.1 -1 TeV
(
¹-parameter has the dimension of mass!
The superpotential contains a mass scale!)
Scale of origin
Forbidden by symmetry
)
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Solve the -problem by introducing an extra singlet
[Another way is to use the Giudice-Masiero mechanism, which I won’t talk about here.]
Introduce a new iso-singlet neutral colorless chiral superfield , coupling together the usual two Higgs doublet superfields.
If S gains a vacuum expectation value we generate an effective -term, automatically of oder the electroweak scale
with
We must also modify the supersymmetry breaking terms to reflect the new structure
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Yukawa terms effective -term
So our superpotential so far is
But this too has a problem – it has an extra U(1) Peccei-Quinn symmetry
Lagrangian invariant under the (global) transformation:
This extra U(1) is broken with electroweak symmetry breaking (by the effective -term)
massless axion!
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Yukawa terms effective -termPQ breaking term
NMSSM Chiral Superfield Content
massless axion!
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The superpotential of the Next-to-Minimal Supersymmetric Standard Model (NMSSM) is
Yukawa terms effective -term
PQ breaking term
We also need new soft supersymmetry breaking terms in the Lagrangian:
[Dine, Fischler and Srednicki][Ellis, Gunion, Haber, Roszkowski, Zwirner]
Modified Higgs sector: 3 CP-even Higgs, 2 CP-odd Higgs (new real and imagnary scalar S)
“ Neutralino sector: 5 neutralinos (new fermion component of S)
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Parameters:
The MSSM limit is ! 0, ! 0, keeping / and fixed.
and are forced to be reasonably small due to renormalisation group running.
Top left entry of CP-odd mass matrix. Becomes MSSM MA in MSSM limit.
minimisation conditions
Finally:
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Supersymmetric Models
Minimal Supersymmetric Standard Model (MSSM)
Next to Minimal Supersymmetric Standard Model (NMSSM)[Dine, Fischler and Srednicki] [Ellis, Gunion, Haber, Roszkowski, Zwirner]
Decouple the axion PQSNMSSM
Alternative solution to Peccei–Quinn symmetry :
Linear S term nMSSM
Eat the axion Z0 models (e.g. USSM, E6SSM)
In the latter we extend the gauge group of the SM with an extra gauged U(1)0!
When U(1)0 is broken as S gets a vev, Z0 eats the masless axion to become massive vector boson!
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Supersymmetric Models
Minimal Supersymmetric Standard Model (MSSM)
Next to Minimal Supersymmetric Standard Model (NMSSM)
Other variants: nmMSSM, PQSNMSSM.
U(1) extended Supersymmetric Standard Model (USSM)
Exceptional Supersymmetric Standard Model (E6SSM)
[Dine, Fischler and Srednicki][Ellis, Gunion, Haber, Roszkowski, Zwirner]
[S.F. King, S. Moretti, R. Nevzrov, Phys.Rev. D73 (2006) 035009]
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Yukawa terms effective -term
USSM Chiral Superfield Content
Problem: to avoid gauge anomalies
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Yukawa terms effective -term
USSM Chiral Superfield Content
Problem: to avoid gauge anomalies
Charges not specified in the definition of the USSM
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U(1) extended Supersymmetric Standard Model (USSM)
Yukawa terms effective -term
Modified Higgs sector: 3 CP-even Higgs, 2 CP-odd Higgs (new real and imagnary scalar S) Modified Neutralino sector: 6 neutralinos: (new singlino + Zprimino )
Modified Gauge sector, new Z0
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Disclaimer: I work on the E6SSM
Final part included for vanity
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For anomaly cancelation, one can use complete E6 matter multiplets
New U(1)0 from E6
E6 inspired models
Matter from 3 complete generations of E6
) automatic cancellation of gauge anomalies!
In the E6SSM ) right-handed neutrino is a gauge singlet
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All the SM matter fields are contained in one 27-plet of E6 per generation.
27
10, 1
5*, 2
5*, - 3
5, - 2
1, 0
+
+
+
+
U(1)N chargeSU(5) reps.
1, 5+ singlets
right handed neutrino
3 generations of “Higgs”
exotic quarks
Exceptional Supersymmetric Standard Model(E6SSM)
[Phys.Rev. D73 (2006) 035009 , Phys.Lett. B634 (2006) 278-284 S.F.King, S.Moretti & R. Nevzorov]
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E6SSM Chiral Superfield Content
Note: In it’s usual form there are also two extra SU(2) doublets included for single step gauge coupling unification, but these are negleected here for simplicity.
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SUSY Theory space
Gauge group(vector
superfields)
Chiral superfieldsMinimal
superfieldsComplete E6 multiplets
E6SSM
MSSMNMSSM
USSM
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Thank you for listening
End of Supersymmetry Lecture course
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Sfermion masses
m2~f L
~f L ~f ¤L + m2
~f R~f ¤R ~f R + Amf ~f L ~f ¤
R
¹ mf u cot ¯ ~f uR ~f uL ¹ mf d tan¯ ~f dR ~f dL(where f u and f d are up and down type fermions respectively)
¢ ~f L~f L ~f ¤
L ¢ ~f R~f R ~f ¤
R
L 3r dgen~f ¡ mass = ¡ (et¤
L et¤R ) m2
etµ etL
etR
¶¡ ¡ eb¤
L et¤R
¢m2eb
µ ebLebR
¶¡ ( e¿¤
L e¿¤R ) m2
e¿µ e¿L
e¿R
¶
where
m2et =
µ m2Q3 + m2
t + ¢ ~uL v(A¤t sin¯ ¡ ¹ yt cos¯)
v(At sin¯ ¡ ¹ ¤yt cos¯) m2u3 + m2
t + ¢ ~uR
¶:
m2et =
µ m2Q3 + m2
b + ¢ ~dL v(A¤t sin¯ ¡ ¹ yt cos¯)
v(At sin¯ ¡ ¹ ¤yt cos¯) m2d3
+ m2t + ¢ ~dR
¶: