THE STATUS OF THE BSM
SCENARIOS
(AFTER THE FIRST LHC PHASE)
STEFAN POKORSKI, UNIVERSITY OF WARSAW
LHC 7-8 TeV
A GREAT TRIUMPH: 125 GeV HIGGS DISCOVERY
A PARTICLE APPARENTLY JUST AS THE
ELEMENTARY HIGGS BOSON PREDICTED
BY THE SM IS DISCOVERED!
„APPARENTLY JUST” IS VERY IMPORTANT!
TO APPRECIATE ALL THAT LET’S REMEMBER THE FOLLOWING….
The Brout-Englert-Higgs mechanism in the
gauge theory of electroweak interactions
needs additional interactions with
spontaneously broken GLOBAL symmetry
e.g
SU(2)xSU(2)SU(2)
The BEH mechanism:
Goldstone bosons become the longitudinal
modes of the gauge bosons W, Z which
acquire masses.
Simplest dynamical sector (considered by many as
a toy model) with global chiral symmetry (to be
spontaneously broken) – self interacting scalar
field, a doublet of SU(2)- IS NOW PROMOTED TO
A REAL THING
3 Goldstone bosons +
physical elementary scalar
IN SM THE HIGGS COUPLINGS TO A PAIR OF FERMIONS OR GAUGE
BOSONS ARE IN PROPORTION TO THEIR MASSES
VERY UNLIKELY TO REPRODUCE
IT BY ACCIDENT
GIARDINO ET AL.’13
IT REALLY APPEARS AS THE
SM HIGGS PARTICLE!
3
AT LEAST AT THE ELECTROWEAK SCALE, THE SM IS A
CORRECT EFFECTIVE THEORY OF ELECTROWEAK
INTERACTIONS
IS THE SM A CONSISTENT THEORY UP TO THE PLANCK
SCALE (LIKE e.g. QED)?
YES!
RENORMALISABLE
NO LANDAU POLE UP TO Mp
(ALMOST) STABLE VACUUM UP TO Mp
THOSE CONCLUSIONS STRONGLY DEPEND ON
THE HIGGS MASS HAPPENS TO BE WELL BELOW THE
PERTURBATIVITY LIMIT AND AT THE EDGE OF THE VACUUM
STABILITY BOUND (FOR THE TOP MASS AROUND 173 GeV) UP TO
THE PLANCK SCALE
IS THE SM A CONSISTENT THEORY UP TO THE PLANCK
SCALE?
YES BUT….
ISNT IT INDEED JUST AN EFFECTIVE THEORY, AN APPROXIMATION
TO A DEEPER ONE
(SIMILARLY AS QED, ALTHOUGH CONSITENT UP TO
Mp, IS ONLY LOW ENERGY APPROXIMATION TO SM)?
BY THE WAY, RENORMALISABILITY IS A GREAT VIRTUE
OF EFFECTIVE THEORIES
INDEED, IN SPITE OF NO HINT FOR NP AT THE LHC,
DONT RUSH TO A TOO QUICK CONCLUSION ON THE
VALIDITY OF THE SM TO PLANCK SCALE BECAUSE:
HIGGS COUPLINGS VERSUS NEW SCALES:
less than (3- 5) % deviations
from the SM couplings
VERY CHALLANGING: DEVIATIONS MAY BE OF THE ORDER OF THE
PRESENT UNCERTAINITIES IN THE SM PREDICTIONS
8
NO MATTER HOW CHALLANGING IT MAY BE
TO SEE BSM PHYSICS THAT WAY,
PRECISION HIGGS (AND TOP) PHYSICS
LOOKS NOW LIKE A MUST!
(CLIC, ILC, FCC?)
9
WHY BSM, IN SPITE OF THE SUCCESS OF SM- CONT…
EMPIRICAL EVIDENCE FOR BSM: DARK MATTER-THIS IS NOW THE CRUCIAL PROBLEM IN PARTICLE
PHYSICS (WITH A PARTICLE PHYSICS SOLUTION?)
IF THERMAL EQUILIBRUM IN THE EARLY UNIVERSE IS
THE SOURCE OF THE DM RELIC ABUNDANCE, THEN THE
VALUE
IS THE MAJOR HINT FOR A LOW SCALE NEW PHYSICS !
+ DIRECT DETECTION + LHC -> RELEVANT PARAMETR SPACE BEGINS TO BE TESTED
11
WHY BSM, IN SPITE OF THE SUCCESS OF SM- CONT…
THE HIGGS PARTICLE WOULD BE THE FIRST
EXAMPLE OF AN ELEMENTARY SCALAR PARTICLE!
So far, Nature does not seem to like elementary scalars
and the composite ones are never „unnaturally” light
(much lighter than the compositeness scale) unless they
are (pseudo) Nambu- Goldstone bosons, like pions in
QCD
NATURALNESS PROBLEM OF THE SM:
ANY SHORT DISTANCE PHYSICS THAT COUPLES TO THE HIGGS
(RH NEUTRINO, GUT PARTICLES..) WOULD INTRODUCE
QUADRATIC SENSITIVITY OF VEV
TO THOSE SCALES
STRICTLY SPEAKING,
IT IS NOT THE PROBLEM OF
QUADRATIC DIVERGENCES IN THE SM:
IF NO SCALES EXCEPT V=240 GEV AND
IGNORING GRAVITY AS A PHYSICAL
CUT-OFF, ONE MAY IGNORE THE
PROBLEM (BECAUSE THE SM IS
RENORMALISABLE)
IN ADDITION,
Higgs potential in the SM: describes but does
not explain dynamically the origin of the Fermi
scale
IF IT HAS A DYNAMICAL EXPLANATION, THE SM SHOULD
BE EMBEDDED IN A DEEPER THEORY!
OTHERWISE, ANTHROPIC PRINCIPLE HAS TO BE INVOKED?
BUT WE NEED ONLY ONE SCALAR. WHAT IF MORE ARE DISCOVERED?
GIVEN THE APPARENT FINAL SUCCESS OF THE SM AND
THE ABSENCE OF ANY EVIDENCE FOR NEW PARTICLES
(SO FAR)—
HAS THE CASE FOR BSM PHYSICS CLOSE TO THE
ELECTROWEAK SCALE CHANGED?
THE MOTIVATION REMAINS INTACT: DARK MATTER AND
THE QUESTION ABOUT THE ORIGIN OF THE FERMI CONSTANT
HOPEFULLY, THE SOLUTION TO THE DM IS PART OF A COMPLETE
BSM THEORY CLOSE TO THE WEAK SCALE BUT IT IS ALSO
CONCEIVEABLE THAT IT IS NOT THE CASE
10
WITH THE ABOVE GUIDELINE, THERE ARE TWO MAIN DIRECTIONS:
SUPERSYMMETRY
COMPOSITE HIGGS MODELS
(HIGGS DOUBLET AS A NAMBU- GOLDSTONE
BOSON OF A NEW STRONG SECTOR WITH A
SUFFICIENTLY BIG SPONTANEOUSLY BROKEN
GLOBAL SYMMETRY E.G. SO(5)SO(4)
BOTH CAN ACCOMMODATE 125 GeV MASS AND
ALMOST SM-LIKE COUPLINGS
14
SUPERSYMMETRY
UNIQUE FEATURE: CANCELLATION OF QUADRATIC SENSITIVITY TO
ARBITRARILY HIGH SCALES
(FERMION – BOSON CANCELLATIONS)
…………..
……….
+
……….
…….
~
15
FOR THE STOP MASS 1 TeV,
SO WE GET 1% FINETUNING IN THE HIGGS POTENTIAL
FERMION – FERMION CANCELLATIONS!
EXP. SIGNATURES: HEAVY FERMIONS, SPIN 1 VECTOR MESONS
16
COMPOSITE MODELS CAN ACCOMMODATE 125 GeV
HIGGS BOSON
BUT, IT’S A PHYSICAL PICTURE RATHER THAN A REAL MODEL
A LOT OF ARBITRARINESS , NO EASY UV COMPLETION,
ELECTROWEAK SECTOR LINKED TO NON-PERTURBATIVE
PHYSICS
ALL THAT CAN BE CONFRONTED WITH THE WELL KNOWN
VIRTUES OF SUPERSYMMETRY
17
MORE RECENTLY, REVIVAL OF THE IDEA OF
CLASSICALLY SCALE INVARIANT SM (BARDEEN-1995)
AT TREE LEVEL; EWSB BY QUANTUM
CORRECTIONS-COLEMAN&WEINBERG
ONLY LOGARITHMIC QUANTUM CORRECTIONS; IGNORING
GRAVITY AS A PHYSICAL CUT-OFF AND IN CONSEQUENCE
IGNORING QUADRATIC DEPENDENCE ON Mp
DIMENSIONAL TRANSMUTATION a LA QCD, EXCEPT THAT
IN QCD THERE IS NO ELEMENTARY SCALAR…
CAN ONE ALSO GET DM AND NEUTRINO MASSES IN SUCH ONE
SCALE MODEL?
TUNING IN MANY DIMENSIONLESS COUPLING?
THEORETICALLY NOT WELL FOUNDED BUT INTRIGUING,
IF A REALISTIC MODELS CAN BE CONSTRUCTED…
TWO THEORIES THAT PREDICT THE HIGGS MASS IN A CERTAIN
NARROW RANGE, AS A FUNCTION OF THE TOP MASS
• SM EXTRAPOLATED TO THE PLANCK MASS
• MINIMAL SUPERSYMMETRIC MODEL
AS A FUNCTION OF THE TOP AND
STOP MASS
TAKE 1 TeV FOR STOPS TO KEEP THE HIGGS POTENTIAL REASONABLY
„NATURAL”
150
140
mh
Low energy MSSM excluded
lity
Instabi
130
120
the
of
SM
110
vacuum
100
120
140
160
m top
180
200
150
140
mh
Low energy MSSM excluded
lity
Instabi
130
120
the
of
SM
110
vacuum
100
120
140
160
m top
180
200
NON OBSERVATION OF THE SUPERPARTNERS IS
CONSISTENT WITH THE HIGGS MASS BUT AT THE
SAME TIME IS PUTTING THE IDEA OF NATURALNESS
UNDER CERTAIN PRESSURE
HOWEVER
SUSY SEARCHERS ARE STILL QUITE FRAGMENTARY
HIDDEN NATURALNESS? ( STEALTH SUPERSYMMETRY)
Searches
for
top
squarks
 Dedicated searches for both direct and indirect production of top squarks;
constraints on top squarks
L
S
P
m
a
s
s
[G
e
V
]
no signs of them
(yet):
Run-1
0
~
~
g
g
p
r
o
d
u
c
tio
n
,~
g
® tt~
c
1
9
0
0 CMS
Preliminary
s = 8 TeV
8
0
0
EPSHEP 2013
Observed
Observed -1 sSUSY
theory
Expected
7
0
0
6
0
0
5
0
0
4
0
0 luino)
g
m(
3
0
0
P)
LS
m(
)
ino
glu
m(
=
+
W)
m(
=2
P)
(LS
-m
SUS-12-024 0-lep ( ET +HT ) 19.4 fb -1
SUS-13-007 1-lep (n
jets
³ 6) 19.4 fb -1
SUS-13-013 2-lep (SS+b) 19.5 fb
-1
SUS-13-008 3-lep (3l+b) 19.5 fb -1
)
top
m(
)
top
m(
2
0
0
1
0
0
0
6
0
07
0
08
0
09
0
01
0
0
01
1
0
01
2
0
01
3
0
01
4
0
01
5
0
0
g
lu
in
o
m
a
s
s
[G
e
V
]
Vigorously
probed
using many
different analyses
 But!
still
room left for
naturalness:
e.g. M(gluino)~1.5
TeV;
m(stop)~300
GeV;pretty
m(LSP)~150
GeVscenarios still allowed, e.g
! However,
natural
 Really need
more energy!
!M(g)=1.5
TeV, m(t)=300 GeV, m(LSP)=150 GeV
! LHC (and HL-LHC) will be able to discover such scenarios
25!
Feb 03, 2014
CERN Accelerator School
27
SUMMARY
THE HIGGS DISCOVERY MAKES THE SM LOOKING AS A
CONSISTENT THEORY UP TO VERY HIGH ENERGIES
BUT THE CASE FOR THE BSM PHYSICS REMAINS INTACT:
DARK MATTER AND DYNAMICAL ORIGIN OF THE FERMI
CONSTANT. MAY OR MAY NOT BE UNDERSTOOD IN ONE
THEORETICAL FRAMEWORK?
SUPERSYMMETRY REMAINS TO BE THE LEADING CANDIDATE
CLASSICALLY SCALE INVARIANT SM (PLUS MINIMAL ADDITIONS)?
THE EXPERIMENTAL EXPLORATION OF THE TeV SCALE IS
STILL IN A VERY PRELIMINARY STAGE
25
END