-
The hunt for new physics at the LHC
• The standard model
• Testing the standard model
• Problems
• Beyond the standardmodel/paradigm
• New physics at the LHC
UCSB, May 2010 Paul Langacker (IAS)
-
The Standard Model
• Standard model: SU(2) × U(1) (extended to include ν masses)+ QCD + general relativity
• Mathematically consistent, renormalizable theory
• Correct to 10−16 cm:– QCD: short distance, long distance symmetries
– QED, WCC, WNC, W , Z
– Gauge self-interactions
• Missing: Higgs (or alternative), dark matter, dark energy
• Complicated, free parameters, fine tunings⇒ must be new physics
UCSB, May 2010 Paul Langacker (IAS)
-
The Fundamental Forces
Strong Electromagnetic Weak Gravity
6
6
6
6
π0
pionn
n
p
p
������������6
6
6
6
G
gluonu
u
d
d
������6
6
6
6
γ
photon
p
p
e−
e−
� � � � � �� � � � � �6
6
������
6 W−
IVB
ν̄ee−
n
p
������6
6
6
6
g
graviton
(spin 2)
V = g2πe−mπr
re2
r g2e−MWr
rGN
m1m2r
strength:g2π4π∼14 α =
e2
4π ∼ 1137 g2E2
M2W
∼ 10−11
(E = 1 MeV)
GNm1m2∼10−38(m1=m2=1 GeV)
range: h̄mπc ∼10−13 cm ≡ 1 fm
∞ h̄MWc
∼ 10−16 cm ∞
UCSB, May 2010 Paul Langacker (IAS)
-
Unification of Forces
Strong Electromagnetic Weak Gravity
hadrons: p, n;pions: π±, π0;(QCD: quarks,gluons)
charged particles:e−, µ−, τ−;p;π±
p, n, π; e, µ, τ ;,neutrinos:νe, νµ, ντ
all particles (alwaysattractive)
nuclear binding;energy in stars
atoms, crystals,molecules; light;chemical energy
decays: n →pe−ν̄e; elementsynthesis
weight; binding ofsolar system, stars,galaxies
← E + B →(Maxwell)
← QCD → ← Electroweak (SU(2)× U(1))→← Grand Unification (GUT)? →← Theory of Everything (superstring)? →
UCSB, May 2010 Paul Langacker (IAS)
-
The Standard Model
• Gauge group SU(3)× SU(2)× U(1); gauge couplings gs, g, g′(ud
)
L
(ud
)
L
(ud
)
L
(νee−
)
L
uR uR uR νeR(?)
dR dR dR e−R
( L = left-handed, R = right-handed)
• SU(3): u ↔ u ↔ u, d ↔ d ↔ d (8 gluons)
• SU(2): uL↔ dL, νeL↔ e−L (W±); phases (W 0)
• U(1): phases (B)
• Heavy families (c, s, νµ, µ−), (t, b, ντ , τ−)
UCSB, May 2010 Paul Langacker (IAS)
-
Quantum Chromodynamics (QCD)
• QCD now very well established
• Short distance behavior (asymptotic freedom)
• Confinement, light hadron spectrum (lattice)– gs = O(1) (αs(MZ) = g2s/4π ∼ 0.12)– Strength + gluon self-interactions ⇒ confinement– Yukawa model ⇒ dipole-dipole
• Approximate global SU(3)L × SU(3)R symmetry and breaking(π,K, η are pseudo-goldstone bosons)
• Unique field theory of strong interactions
UCSB, May 2010 Paul Langacker (IAS)
-
Quasi-Chiral Exotics
(J. Kang, PL, B. Nelson, in progress)
• Exotic fermions (anomaly-cancellation)
• Examples in 27-plet of E6– DL + DR (SU(2) singlets, chiral wrt U(1)′)
–
(E0
E−
)
L
+
(E0
E−
)
R
(SU(2) doublets, chiral wrt U(1)′)
• Pair produce D + D̄ by QCD processes (smaller rate for exotic leptons)
• Lightest may decay by mixing; by diquark or leptoquark coupling;or be quasi-stable
22nd Henry Primakoff Lecture Paul Langacker (3/1/2006)
Quantum Chromodynamics (QCD)
Modern theory of the strong interactions
NYS APS (October 15, 2004) Paul Langacker (Penn)
9. Quantum chromodynamics 7
0.1 0.12 0.14
Average
Hadronic Jets
Polarized DIS
Deep Inelastic Scattering (DIS)
! decays
Z width
Fragmentation
Spectroscopy (Lattice)
ep event shapes
Photo-production
" decay
e+e
- rates
#s(M
Z)
Figure 9.1: Summary of the value of αs(MZ) from various processes. The valuesshown indicate the process and the measured value of αs extrapolated to µ = MZ .The error shown is the total error including theoretical uncertainties. The averagequoted in this report which comes from these measurements is also shown. See textfor discussion of errors.
theoretical estimates. If the nonperturbative terms are omitted from the fit, the extractedvalue of αs(mτ ) decreases by ∼ 0.02.
For αs(mτ ) = 0.35 the perturbative series for Rτ is Rτ ∼ 3.058(1+0.112+0.064+0.036).The size (estimated error) of the nonperturbative term is 20% (7%) of the size of theorder α3s term. The perturbation series is not very well convergent; if the order α3s termis omitted, the extracted value of αs(mτ ) increases by 0.05. The order α4s term has beenestimated [47] and attempts made to resum the entire series [48,49]. These estimates canbe used to obtain an estimate of the errors due to these unknown terms [50,51]. Anotherapproach to estimating this α4s term gives a contribution that is slightly larger than theα3s term [52].
Rτ can be extracted from the semi-leptonic branching ratio from the relationRτ = 1/(B(τ → eνν) − 1.97256); where B(τ → eνν) is measured directly or extractedfrom the lifetime, the muon mass, and the muon lifetime assuming universality of lepton
December 20, 2005 11:23
18 9. Quantum chromodynamics
0
0.1
0.2
0.3
1 10 102
µ GeV!
s(µ
)
Figure 9.2: Summary of the values of αs(µ) at the values of µ where they aremeasured. The lines show the central values and the ±1σ limits of our average.The figure clearly shows the decrease in αs(µ) with increasing µ. The data are,in increasing order of µ, τ width, Υ decays, deep inelastic scattering, e+e− eventshapes at 22 GeV from the JADE data, shapes at TRISTAN at 58 GeV, Z width,and e+e− event shapes at 135 and 189 GeV.
The value of αs at any scale corresponding to our average can be obtainedfrom http://www-theory.lbl.gov/∼ianh/alpha/alpha.html which uses Eq. (9.5) tointerpolate.
References:1. R.K. Ellis et al., “QCD and Collider Physics” (Cambridge 1996).2. For reviews see, for example, A.S. Kronfeld and P.B. Mackenzie, Ann. Rev. Nucl.
and Part. Sci. 43, 793 (1993);H. Wittig, Int. J. Mod. Phys. A12, 4477 (1997).
3. For example see, P. Gambino, International Conference on Lepton PhotonInteractions, Fermilab, USA, (2003); J. Butterworth International Conference onLepton Photon Interactions, Upsala, Sweden, (2005).
December 20, 2005 11:23
UCSB, May 2010 Paul Langacker (IAS)
-
Quantum Electrodynamics (QED)
Experiment Value of α−1 Precision ∆eae = (ge − 2)/2 137.035 999 683 (94) [6.9× 10−10] –h/m (Rb, Cs) 137.035 999 35 (69) [5.0× 10−9] 0.33± 0.69Quantum Hall 137.036 003 0 (25) [1.8× 10−8] −3.3± 2.5h/m (neutron) 137.036 007 7 (28) [2.1× 10−8] −8.0± 2.8γp,3He
(J. J.) 137.035 987 5 (43) [3.1× 10−8] 12.2± 4.3
µ+e− hyperfine 137.036 001 7 (80) [5.8× 10−8] −2.0± 8.0
Spectacularly successful:
Most precise: e anomalous magnetic moment → αMany low energy tests to few ×10−8mγ < 6× 10−17 eV, qγ < 5× 10−30|e|Running α(Q2) observed
Muon g − 2 sensitive to new physics. Anomaly?
UCSB, May 2010 Paul Langacker (IAS)
-
The Electroweak Theory
• QED and weak chargedcurrent unified
• Weak neutral current (Z)predicted(νN → νX, atomic parityviolation)
• Stringent tests of WCC,CP -violation, WNC, Z-pole, beyond
• Fermion gauge and gaugeself-interactions
f
f
γ
−ieqf γµf
f
Z
−i g2 cos θW
γµ(gfV− gf
Aγ5)
dj
ui
W+
−i g2√
2γµ(1− γ5)Vqij
– Typeset by FoilTEX – 1
→W−
−ig2√
2Jν†W
−ig2√
2JµW
Z
−ig2 cos θW
JνZ−ig
2 cos θWJµZ
– Typeset by FoilTEX – 1
νe
W− W +
e− e+
γ
W− W +
e− e+
Z
W− W +
e− e+
– Typeset by FoilTEX – 1
UCSB, May 2010 Paul Langacker (IAS)
-
10
10 2
10 3
10 4
10 5
0 20 40 60 80 100 120 140 160 180 200 220
Centre-of-mass energy (GeV)
Cro
ss-s
ecti
on (
pb)
CESRDORIS
PEP
PETRATRISTAN
KEKBPEP-II
SLC
LEP I LEP II
Z
W+W-
e+e−→hadrons
γ
α
α
dm∆
Kε
Kε
sm∆ & dm∆
ubV
βsin 2(excl. at CL > 0.95)
< 0βsol. w/ cos 2
α
βγ
ρ-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
η
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
excl
uded
are
a ha
s C
L >
0.9
5
ICHEP 08
CKMf i t t e r
0
10
20
30
160 180 200
!s (GeV)
"W
W (
pb
)
YFSWW/RacoonWW
no ZWW vertex (Gentle)
only #e exchange (Gentle)
LEPPRELIMINARY
17/02/2005
UCSB, May 2010 Paul Langacker (IAS)
-
• SM correct and unique to zerothapprox. (gauge principle, group,representations)
• SM correct at loop level (renormgauge theory; mt, αs, MH)
• TeV physics severely constrained(unification versus compositeness)
• Consistent with light elementaryHiggs
• Precise gauge couplings (SUSYgauge unification)
1. Electroweak model and constraints on new physics 15
0.0001 0.001 0.01 0.1 1 10 100 1000 10000µ [GeV]
0.228
0.23
0.232
0.234
0.236
0.238
0.24
0.242
0.244
0.246
0.248
0.25
sin2 !
W(µ
)
QW(APV)QW(e)
"-DIS
LEP 1
SLC
Tevatron
e-DIS
MOLLER
Qweak
Figure 1.1: Scale dependence of the weak mixing angle defined in the MSscheme [128] (for the scale dependence of the weak mixing angle defined in amass-dependent renormalization scheme, see Ref. 125). The minimum of the curvecorresponds to Q = MW , below which we switch to an effective theory withthe W± bosons integrated out, and where the β-function for the weak mixingangle changes sign. At the location of the W boson mass and each fermion mass,there are also discontinuities arising from scheme dependent matching terms whichare necessary to ensure that the various effective field theories within a givenloop order describe the same physics. However, in the MS scheme these are verysmall numerically and barely visible in the figure provided one decouples quarksat Q = m̂q(m̂q). The width of the curve reflects the theory uncertainty fromstrong interaction effects which at low energies is at the level of ±7 × 10−5 [128].Following the estimate [129] of the typical momentum transfer for parity violationexperiments in Cs, the location of the APV data point is given by µ = 2.4 MeV.For ν-DIS we chose µ = 20 GeV which is about half-way between the averages of√
Q2 for ν and ν interactions at NuTeV. The Tevatron measurements are stronglydominated by invariant masses of the final state dilepton pair of O(MZ) and canthus be considered as additional Z pole data points, yielding s̄2Z = 0.2316 ± 0.0018.However, for clarity we displayed the point horizontally to the right.
E.g., QW (133Cs) is extracted by measuring experimentally the ratio of the parity violating
amplitude, EPNC, to the Stark vector transition polarizability, β, and by calculating
April 28, 2010 15:17
Measurement Fit |Omeas−Ofit|/σmeas0 1 2 3
0 1 2 3
∆αhad(mZ)∆α(5) 0.02758 ± 0.00035 0.02768
mZ [GeV]mZ [GeV] 91.1875 ± 0.0021 91.1874ΓZ [GeV]ΓZ [GeV] 2.4952 ± 0.0023 2.4959σhad [nb]σ
0 41.540 ± 0.037 41.478RlRl 20.767 ± 0.025 20.742AfbA
0,l 0.01714 ± 0.00095 0.01645Al(Pτ)Al(Pτ) 0.1465 ± 0.0032 0.1481RbRb 0.21629 ± 0.00066 0.21579RcRc 0.1721 ± 0.0030 0.1723AfbA
0,b 0.0992 ± 0.0016 0.1038AfbA
0,c 0.0707 ± 0.0035 0.0742AbAb 0.923 ± 0.020 0.935AcAc 0.670 ± 0.027 0.668Al(SLD)Al(SLD) 0.1513 ± 0.0021 0.1481sin2θeffsin
2θlept(Qfb) 0.2324 ± 0.0012 0.2314mW [GeV]mW [GeV] 80.399 ± 0.023 80.379ΓW [GeV]ΓW [GeV] 2.098 ± 0.048 2.092mt [GeV]mt [GeV] 173.1 ± 1.3 173.2
August 2009
UCSB, May 2010 Paul Langacker (IAS)
-
The Higgs Mechanism
• Gauge symmetry forbids elementary masses for W , Z, fermions
• Introduce Higgs field H, with classical value ν and potential energyV (ν) = 1
2µ2ν2 + 1
4λν4
• W , Z, fermions acquire effective masses by coupling to H(transparent to photon)
φ
ν−ν
V (φ)
W
W
ν
ν
g2
eR
eL
νhe
– Typeset by FoilTEX – 1
W
W
ν
ν
g2
eR
eL
νhe
– Typeset by FoilTEX – 1
UCSB, May 2010 Paul Langacker (IAS)
-
• Higgs mass MH =√−2µ2 =√
2λν (ν ∼ 246 GeV, λ unknown)
• LEP search e+e− → Z∗ →ZH: MH > 114.4 GeV
• Indirect (electroweak radiativecorrections)) + direct: MH <149 GeV (95%)
• Tevatron searches nowsensitive enough for highermasses
• LHC will cover full range forstandard model Higgs
145 150 155 160 165 170 175 180 185 190mt [GeV]
10
20
30
50
100
200
300
500
1000
MH [
GeV
]
LEP 2
Tevatron excluded (95% CL)
excluded
all data (90% CL)
(95% CL)
ΓZ, σ
had, R
l, R
q
Z pole asymmetriesMWlow energymt
1
10
100 110 120 130 140 150 160 170 180 190 200
1
10
mH(GeV/c2)
95%
CL
Lim
it/S
M
Tevatron Run II Preliminary, L=0.9-4.2 fb-1
ExpectedObserved±1σ Expected±2σ Expected
LEP Exclusion TevatronExclusion
SMMarch 5, 2009
UCSB, May 2010 Paul Langacker (IAS)
-
Problems with the Standard Model
Lagrangian after symmetry breaking:
L = LQCD + Lgauge + LHiggs +∑
i
ψ̄i
(i 6∂ −mi −
miH
ν
)ψi
− g2√
2
(JµWW
−µ + J
µ†WW
+µ
)− eJµQAµ −
g
2 cos θWJµZZµ
Standard model: SU(2) × U(1) (extended to include ν masses) +QCD + general relativity
Mathematically consistent, renormalizable theory
Correct to 10−16 cm
UCSB, May 2010 Paul Langacker (IAS)
-
However, too much arbitrariness and fine-tuning: O(27) parameters(+ 2 for Majorana ν) and electric charges
• Gauge Problem– complicated gauge group with 3 couplings (only EW chiral)
– charge quantization (|qe| = |qp|) unexplained– Possible solutions: strings; grand unification; magnetic
monopoles (partial); anomaly constraints (partial)
• Fermion problem– Fermion masses, mixings, families unexplained
– Neutrino masses, nature? Probe of Planck/GUT scale?
– CP violation inadequate to explain baryon asymmetry
– Possible solutions: strings; brane worlds; family symmetries;compositeness; radiative hierarchies. New sources of CPviolation.
UCSB, May 2010 Paul Langacker (IAS)
-
• Higgs/hierarchy problem– Expect M2H = O(M
2W )
– higher order corrections:δM2H/M
2W ∼ 1034
H
H Hλ
W
H Hg2
W
W
H Hg g
f
f
H Hh h
– Typeset by FoilTEX – 1
Possible solutions: supersymmetry; dynamical symmetry breaking;large and/or warped extra dimensions; Little Higgs; anthropicallymotivated fine-tuning (split supersymmetry) (landscape)
• Strong CP problem– Can add θ
32π2g2sF F̃ to QCD (breaks, P, T, CP)
– dN ⇒ θ < 10−11, but δθ|weak ∼ 10−3– Possible solutions: spontaneously broken global U(1) (Peccei-
Quinn) ⇒ axion; unbroken global U(1) (massless u quark);spontaneously broken CP + other symmetries
UCSB, May 2010 Paul Langacker (IAS)
-
• Graviton problem– gravity not unified
– quantum gravity not renormalizable
– cosmological constant: ΛSSB = 8πGN〈V 〉 > 1050Λobs(10124 for GUTs, strings)
Possible solutions:
– supergravity and Kaluza Klein unify
– strings yield finite gravity
– Λcosm = Λbare + ΛSSB. Anthropically motivated fine-tuning(landscape)?
UCSB, May 2010 Paul Langacker (IAS)
-
Necessary new ingredients
• Mechanism for small neutrino masses– Planck/GUT scale? Small Dirac (intermediate scale)?
• Mechanism for baryon asymmetry?– Electroweak transition (Z′ or extended Higgs?)– Heavy Majorana neutrino decay (seesaw)?
– Decay of coherent field? CPT violation?
• What is the dark energy?– Cosmological Constant? Quintessence?
– Related to inflation? Time variation of couplings?
UCSB, May 2010 Paul Langacker (IAS)
-
• What is the dark matter? (Recent anomalies in e+/e−, DAMA, etc?)– Lightest supersymmetric particle (LSP)? Axion? Gravitino?
Primordial black hole? SuperWIMP?
– “Ad hoc” weakly coupled dark sector?
• Suppression of flavor changing neutral currents? Proton decay?Electric dipole moments?
– Automatic in standard model, but not in extensions(“particle Fermi paradox” a.k.a. little hierarchy problem)
UCSB, May 2010 Paul Langacker (IAS)
-
New Physics
• A new layer at the TeV scale– Compositeness, Little Higgs, twin Higgs, Higgless, dynamical
symmetry breaking, strong dynamics
– Precision electroweak constraints, FCNC, UV completions?
• Large and/or warped extra dimensions; possible low fundamentalor string scale
• Unification at the Planck scale, MP = G−1/2N ∼ 1019 GeV– Supersymmetry (between fermions and bosons), grand unification,
strings?
– Top-down remnants: Z′, W ′, extended Higgs, exotic fermions,· · ·
UCSB, May 2010 Paul Langacker (IAS)
-
Compositeness, Strong Dynamics
• Composite fermions, scalars (onion-like layers)– Not like to atom → nucleus +e− → p+ n→ quark
• Alternative electroweak breaking: Little Higgs, dynamicalsymmetry breaking, topcolor, · · ·
• At most one more layer accessible (Tevatron, LHC, ILC)
• Rare decays (e.g., K → µe)
• Usually few % effects at LEP/SLC, LEP2, WNC (challenge for models)
• LHC: anomalous V V V , new particles, strong WW →WW
• Also: FCNC, EDM
UCSB, May 2010 Paul Langacker (IAS)
-
Extra dimensions (deconstruction, brane worlds)
• Motivated by strings
• Can be large, warped, stringy
• Matter can be trapped onbranes, at boundaries, or inbulk
• E.g., new dimensions muchlarger than M−1P ∼ 10−33 cm
• Fundamental scale: MF ∼(1 − 100) TeV � M̄Pl =1/√
8πGN ∼ 2.4× 1018 GeV
– Assume δ extra dimensionswith volume Vδ � M−δF
M̄2Pl = M2+δF Vδ �M2F
(but new hierarchy problem)
illustrates the effect. The additional volume provided by the extra dimension(s), asssumed to beaccessible only to the gravitational interaction, would normally allow most of the real strengthof gravity to disappear into the extra dimension(s), but would have the effect of making gravitybecome anomalously strong for sufficiently small separations, indicating that the “true” Planckmass could be as small as a few TeV[48]. Others[49] have suggested that an extra time dimensionwould cause a weakening of gravity at small separations.
Figure 6: Cartoon illustrating the effect of a curled-up large extra dimension on the gravitational force.The cartoon shows one ordinary dimension and one curled up extra dimension. All non-gravitationalphysics is assumed to be confined to the ordinary dimension, and only gravity can expand into the extradimension. The gravitational lines of force from a point mass placed on our x-axis (which runs fromleft to right) are shown. As we probe the gravitational force by moving away from the point mass alongthe x axis, we find that for separations small compared to the radius R of the curled-up dimension, thelines of force diverge, i.e. a 1/r force (Gauss’s Law in 2 dimensions). But as we move along the x axisfarther from the point mass the lines cannot expand any further and become parallel, i.e. a constantforce (Gauss’s Law in 1 dimension.) The transition from constant to 1/r force laws is smooth, and iswell approximated by an additional Yukawa term as long as r > R (see citations in Ref. [2]). Figurecourtesy of Savas Dimopoulos.
• The cosmological constant problem. The observed gravitating vacuum-energy density is vanish-ingly small compared to the predictions of quantum mechanics. The gravitating energy densityρvac ∼ 0.7ρc, inferred from a wide variety of astrophysical observations[1, 50, 51], is at least 1060times smaller (if supersymmetry is “just around the corner”) and possibly 10120 times smaller(if supersymmetry is not valid) than the predicted zero-point energy for a cutoff of MP . The
observed energy density corresponds to a length scale Rvac =4
√h̄c/ρvac ≈ 85 µm and an energy
of 4√
(h̄c)3ρvac ≈ 2 meV that may have fundamental significance[52]. It has been suggested thatthe apparent inability of gravity to “see” the vacuum energy could be explained if the effectivetheory of gravity had a cutoff of ∼ 1 meV[53], so that gravity would effectly “shut off” at lengthscales less than Rvac.
Experimental tests of the gravitational ISL also probe speculations about “non-gravitational” par-ticle physics. It is widely believed that the Standard Model of particle physics cannot be complete.Many ideas for extending the Standard Model predict very-low-mass scalar or vector bosons that wouldproduce short-range exchange forces which could appear as violations of the ISL. Reference [2] providesa recent, comprehensive review of these theoretical motivations. Since the publication of Ref. [2], twonew theoretical proposals with particular relevance to ISL tests have appeared.
• String theories generically predict scalar particles (the dilaton and large numbers of moduli) thatare initially massless. Essentially massless scalar fields are also frequently invoked by cosmologists.However, the exchange forces these bosons mediate would produce apparent violations of theequivalence principle that are not consistent with the extremely tight constraints from laboratorytests discussed above. The “chameleon mechanism” was recently invented[54] to “hide” such
16
UCSB, May 2010 Paul Langacker (IAS)
-
• LHC: Kaluza-Klein excitations,string excitations, gravitonemission, black holes
• Astrophysics
• Macroscopic gravity effects
Figure 10: Constraints on Yukawa violations of the gravitational 1/r2 law for λ ≤ 1 cm. The shadedregion is excluded at the 95% confidence level. Heavy lines labeled Eöt-Wash, Irvine, Wuhan, Col-orado and Stanford show experimental constraints from Refs. [61, 62], [69, 70], [59], [71] and [72, 73],respectively. Lighter lines show various theoretical expectations summarized in Ref. [2].
Figure 11: Constraints on Yukawa violations of the gravitational 1/r2 law for λ ≥ 1 cm. The shadedregion is excluded at the 95% confidence level. Laboratory constraints are from Refs. [69, 70, 74];geophysical and astronomical constraints are taken from an earlier review[2]. The LLR constraint isextracted from current published work[27] but is expected to improve in the future.
21
UCSB, May 2010 Paul Langacker (IAS)
-
Unification
• Unification of interactions
• Grand desert to unification (GUT) or Planck scale
• Elementary Higgs, supersymmetry (SUSY), GUTs, strings
• Possibility of probing to MP and very early universe
UCSB, May 2010 Paul Langacker (IAS)
-
Supersymmetry
• Fermion ↔ boson symmetry
• Motivations– Incorporation of gravity (but MSUSY could be very large)
– Stabilization of electroweak scale
tL
tR
H Hht ht
φr
H Hλr
φr
φr
H Hκr κr
– Typeset by FoilTEX – 1
But landscape ideas (anthropically-motivated fine tuning);
variants (e.g., split supersymmetry); alternative EWSB
UCSB, May 2010 Paul Langacker (IAS)
-
– Gauge unification
– Cold dark matter (LSP) if R-parity (RP ) conserved
– Z-pole: any new physics decouples
– Radiative electroweak breaking (large mt → m2Hu < 0)– Anomalous magnetic moment of muon (gµ − 2)?
µ̃
χ̃0
µ̃
µ µ
γ
χ̃−
ν̃
χ̃−
µ µ
γ
– Typeset by FoilTEX – 1
UCSB, May 2010 Paul Langacker (IAS)
-
• Additional charged and neutral Higgs particles– M2
H0< cos2 2βM2Z+ H.O.T. (O(m
4t)) < (130 GeV)
2, consistent withLEP (standard model: MH0 < 1000 GeV)
– CDF/D0 searches for heavier states
– LHC ultimately sensitive to entire range
160 165 170 175 180 185
mt [GeV]
80.20
80.30
80.40
80.50
80.60
80.70
MW
[G
eV
]
SM
MSSM
MH = 11
4 GeV
MH = 40
0 GeV
light SUSY
heavy SU
SY
SM
MSSM
both models
Heinemeyer, Hollik, Stockinger, Weber, Weiglein ’07
experimental errors 95% CL:
LEP2/Tevatron (today)
LEP2/Tevatron (8 fb-1
)
8 fb-1
: !mt = 1.2 GeV, !M
W = 20 MeV
• Simplest version: supersymmetric contribution to Higgs mass mustbe of O(100) GeV (not 1019) (µ problem)
UCSB, May 2010 Paul Langacker (IAS)
-
• Superpartners– q ⇒ q̃ (scalar quark)– `⇒ ˜̀ (scalar lepton)– H ⇒ H̃ (Higgsino)– G,W,B ⇒ G̃, W̃ , B̃ (gauginos)
– typical scale: several hundredGeV
– LSP: dark matter candidate
– SUSY breaking ⇔ large mt– May be large FCNC, EDM,
∆(gµ − 2)0
100
200
300
400
500
600
700
800
m [GeV]
l̃R
l̃Lν̃l
τ̃1
τ̃2
χ̃01
χ̃02
χ̃03χ̃04
χ̃±1
χ̃±2
ũL, d̃RũR, d̃L
g̃
t̃1
t̃2
b̃1
b̃2
h0
H0, A0 H±
UCSB, May 2010 Paul Langacker (IAS)
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Tevatron, LHC Signatures
• Squarks, gluinos pair-produced at largerate by QCD
• Sleptons, charginos, neutralinos: smallerdirect rate (Drell-Yan and t-channelsquark), but occur in squark decay chains
• Missing transverse energy: decay chainsend in LSP (e.g., χ̃01 in supergravity)
• Cascade decays → multiple jets andleptons (same/opposite sign dileptons,trileptons); kinematic edges (masseigenstates); some spin information
• Same sign leptons ↔ Majorana fermions
0 500 1000 1500 2000 250010
102
103
104
105
Me� (GeV)
Events=50GeV=10 fb�1
Meff = 6ET + Σ4i=1piT
q̃L χ̃02
q1 `�2˜̀�R
`�1χ̃01
UCSB, May 2010 Paul Langacker (IAS)
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• LHC reach at 7 TeV (Baer, Barger, Lessa, Tata, 1004.3594)
(GeV)0
m500 1000 1500 2000 2500
(G
eV
)1
/2m
100
200
300
400
500
600
500 GeV
600 GeV
800 GeV
1 TeV
1.2 TeV
111 GeV
114 GeV
LHC7 - All Channels
LS
Pτ∼
LEP excluded
(G
eV
)g~
m
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
(GeV)0
m500 1000 1500 2000 2500
(G
eV
)1
/2m
100
200
300
400
500
600
-12 fb-11 fb
-10.33 fb-10.1 fb
g~m
hm
= 172.6 GeVt
> 0, mµ = 45, β = 0, tan0A
UCSB, May 2010 Paul Langacker (IAS)
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Grand Unification
• Unify strong SU(3) andelectroweak SU(2)×U(1) insimple group (e.g., SU(5),SO(10), E6), broken at ∼1016 GeV
• Gauge unification (only insupersymmetric version)
0 2 4 6 8 10 12 14 16 18 20
log10
µ (GeV)
02
04
06
08
01
00
!i-1
!1
"1
!2
"1
!3
"1
!1
"1
!2
"1
!3
"1
0 2 4 6 8 10 12 14 16 18 20
log10
µ (GeV)
02
04
06
08
01
00
!i-1
Standard Model
Supersymmetric Standard Model
MSUSY
= MZ
UCSB, May 2010 Paul Langacker (IAS)
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• Seesaw model for small mν (butwhy are mixings large?)
• Quark-lepton (q − l) unification(⇒ charge quantization)
• q − l mass relations (work only forthird family in simplest versions)
• Proton decay? (simplest versionsexcluded)
• Doublet-triplet problem?
• String embedding? (breaking,families may be entangled in extra
dimensions)
1636
mode exposure !Bm observed B.G. (ktï yr) (%) event
p " e+ + #
092 40 0 0.2 54
p " µ+ + #
092 32 0 0.2 43
p " e+ + $ 92 17 0 0.2 23
p " µ+ + $ 92 9 0 0.2 13
n " %__
+ $ 45 21 5 9 5.6p " e
+ + & 92 4.2 0 0.4 5.6
p " e+ + ' 92 2.9 0 0.5 3.8
p " e+ + ( 92 73 0 0.1 98
p " µ+ + ( 92 61 0 0.2 82
p " %__
+ K+
92 22K
+"%µ
+ (spectrum) 34 -- -- 4.2
prompt ( + µ+
8.6 0 0.7 11K
+"#
+#
0 6.0 0 0.6 7.9
n " %__
+ K0
92 2.0K
0"#
0#
0 6.9 14 19.2 3.0
K0"#
+#
- 5.5 20 11.2 0.8
p " e+ + K
092 10.7
K0"#
0#
0 9.2 1 1.1 8.7
K0"#
+#
-
2-ring 7.9 5 3.6 4.0 3-ring 1.3 0 0.1 1.7
p " µ+ + K
092 13.9
K0"#
0#
0 5.4 0 0.4 7.1
K0"#
+#
-
2-ring 7.0 3 3.2 4.9 3-ring 2.8 0 0.3 3.7
1031
1032
1033
1034
p " e+ #
0
e+ $
e+ '
e+ &
0
e+ K
0
µ+ #
0
µ+ $
µ+ '
µ+ &
0
µ+ K
0
%__
#+
%__
&+
%__
K+
n " e+ #
-
e+ &
-
µ+ #
-
µ+ &
-
%__
#0
%__
$%__
'%__
&0
%__
K0
lifetime limit (years)
KAMIMB3SK
Soudan2
Fig. 1. The obtained lifet ime limit of nucleons from SK–I (left figure) and their
comparisons with other experiments (right figure).
6. References
1. J. Ellis et al., Nucl. Phys. B202, 43 (1982)
2. Y.Fukuda et al., Phys. Rev. Let t . 81, 1562 (1998)
3. Y.Fukuda et al., Nucl. Instr. Meth. A501, 418 (2003)
4. H. Georgi and S. L. Glashow, Phys. Rev. Let t . 32, 438 (1974)
5. Y. Hayato et al., Phys. Rev. Let t . 83, 1529 (1999)
6. Jogesh C. Pat i and Abdus Salam, Phys. Rev. Let t . 31, 661 (1973)
7. For example, Jogesh C. Pat i, hep-ph/ 0005095.
8. N. Sakai and T. Yanagida, Nucl. Phys. B197, 533 (1982)
9. M. Shiozawa et al., Phys. Rev. Let t . 81, 3319 (1998)
10. M. Shiozawa, PhD thesis, University of Tokyo (1999)
11. S. Weinberg, Phys. Rev. D26, 287 (1982)
UCSB, May 2010 Paul Langacker (IAS)
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Superstrings
• Finite, “parameter-free” “theoryof everything” (TOE), includingquantum gravity
– 1-d string-like object
– Appears pointlike for resolution> M−1s ∼M−1P ∼ 10−33 cm
– Vibrational modes→ particles– 10 space-time dimensions → 6
must compactify to scale M−1s
– 4-dim supersymmetric gaugetheory below Ms
– May also be solitons (branes),terminating open strings
Intersecting Brane Worlds – A Path to the Standard Model? 5
a
b
Gauge bosons in adj.
Chiral matter in (N, M̄)
The open string spectrum on these intersecting branes contains the following fields [52]:
(i) N = 4 gauge bosons in adjoint representation of U(N) × U(M).(ii) Massless fermions in the chiral (N, M̄) representation.
(iii) In general massive scalar fields, again in the (N, M̄) representation.
The latter two fields originate from open strings stretching from one stack of Dp-
branes to the other one. Since the scalar fields are in general massive, such a
intersecting D-brane configurations generically breaks all space-time supersymmetries.This supersymmetry breaking manifests itself as the a massive/tachyonic scalar ground
state with mass:
M2ab =1
2
∑I
∆ΦIab − max{∆ΦIab} . (4)
(ΦIab is the angle between stacks a and b in some spatial plane I.) Only if the
intersection angles take very special values, some of the scalars become massless, and
some part of space-time supersymmetry gets restored. Specifically consider two special
flat supersymmetric D6-brane configurations, as shown in the following figure:
x x
4
5
6
7
8
9
Φ1
Φ2 Φ3
Supersymmetry now gets restored for the following choice of angles:
• 2 D6-branes, with common world volume in the 123-directions, being parallel inthe 4-5, 6-7 and 8-9 planes:
1/2 BPS (N = 4 SUSY): Φ1 = Φ2 = Φ3 = 0 .• 2 intersecting D6-branes, with common world volume in the 123-directions, and
which intersect in 4-5 and 6-7 planes, being parallel in 8-9 plane:
UCSB, May 2010 Paul Langacker (IAS)
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• Problems– Which type? Dualities
– Which compactification manifold?
– Relation to supersymmetric standard model, GUT?
– Supersymmetry breaking/mediation? Scale? Cosmologicalconstant?
– Many moduli/vacua. Landscape ideas - any predictability left?(TOE⇒TOA?)
• The great debate: is our physics environmental or selected?– Small cosmological constant, weak scale appear needed for life
– Physics depends on location in multiverse? i.e., O(10500) vacuaof landscape continually sampled by pockets of eternally inflatingmultiverse!
UCSB, May 2010 Paul Langacker (IAS)
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Remnant Physics from the Top-Down
• Z′ or other gauge (µ problem, electroweak baryogenesis, · · ·)
• Extended Higgs/neutralino (doublet, singlet)(cascades, dark matter,· · ·)
• Quasi-Chiral Exotics (may be quasi-stable)
• Quasi-hidden (SUSY breaking? Dark sector? Composite family?)
• Non-seesaw mν• LED/low Ms (Kaluza Klein/string excitations, TeV black holes)
• Charge 1/2 (Confinement?, Stable relic?)
• Time varying couplings
• LIV, VEP (e.g., vmax, decays (oscillations) of HE γ, e, gravity waves (ν’s))
UCSB, May 2010 Paul Langacker (IAS)
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Conclusions
• The standard model is approximately correct description offermions/gauge bosons down to ∼ 10−16 cm ∼ 11 TeV (but EWSB?)
• Standard model is complicated/fine-tuned→ must be new physics
• Precision tests severely constrain new TeV-scale physics
• Promising theoretical ideas at Planck scale
• Promising experimental program at LHC (also flavor, ν, cosmology)
• Challenge to make contact between theory and experiment
• Many semi-realistic string constructions suggest extended gauge,Higgs, neutralino, fermion sectors, alternative mν
UCSB, May 2010 Paul Langacker (IAS)