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The hidden dimensions of the Universe

I. Antoniadis

CERN

Joint Physics Colloquia, Taipei, 19 November 2013

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Particle physics:

structure of matter & fundamental forces

Experimental tools: Particle colliders at very high energies =>

physical laws of nature at very short distances LEP2 (CERN): electron - positron collisions at 200 GeV→ 10−15 cm TEVATRON (USA): protons - antiprotons at 2 TeV→ 10−16 cm LHC (CERN):proton - proton collisions at 14 TeV → 10−17 cm

Th description: simple mathematical theories with predictive power encoding the symmetries of physical phenomena

for the moment 8 TeV

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at Accelerating Science and Innovation

the Large Hadron Collider (LHC)

•   Largest scientific instrument ever built, 27km of circumference

•   >10 000 people involved in its

design and construction

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superconducting magnets at 1.9o K => accelerate protons at 0.99999999c orbit LHC ring 11000 times/sec => several thousand billion protons

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A billion p-p collisions per second

each collision has over a thousand particles produced

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… and also a telescope The LHC is the worlds most

powerful microscope …

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Big Bang

Evolution of the Universe

Today 13.8 Billion Years

1028 cm

Only particle

physics can

tell us what

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Standard Model of electroweak + strong forces

Quantum Field Theory Quantum Mechanics + Special Relativity Principle: gauge invariance U(1) × SU(2)×SU(3)

Very accurate description of physics at present energies 17 parameters

1 mediators of gaugeinteractions(vectors): photon, W±, Z +8 gluons

2 matter(fermions): (leptons + quarks) × 3

electron, positron, neutrino (up, down)3 colors

3 Higgs sector: new scalar(s) particle(s):

break the EW symmetryU(1) × SU(2) → U(1)γ at MW ∼ 100 GeV generate mass for all elementary particles Brout-Englert Higgs 1964

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Excellent LHC performance

Number of events = Cross section × Luminosity

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July 4

th

2012 The discovery of a

new particle

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Possible Higgs boson events

!"!"#$"

%&'()(&*$"

!"!"##"

$%&'('%)*"

(18)

Higgs boson discovery at the LHC

mH = 125.9 ± 0.4 GeV(average of Particle Data Group 2013)

(19)

Couplings of the new boson vs SM Higgs

Agreement with Standard Model Higgs expectation at 1.5 σ Most compatible with scalar 0+ hypothesis

Measurement of its properties and decay rates currently under way

(20)

Fran¸cois Englert Peter Higgs Nobel Prize of Physics 2013

↓ ↓

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Why Beyond the Standard Model?

Experimental indications:

Neutrino masses

Unification of gauge couplings ? Dark matter[23]

Two main theory reasons:

Include gravity Quantum Mechanics + General Relativity ? [25]

Mass hierarchy: MW/MPlanck ≃ 10−17[26]

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Gauge coupling unification

Energy evolution of gauge couplings αi = gi2/4π =>

low energy data → extrapolation at high energies:

(23)

Observable Universe

Ordinary baryonic matter: only a tiny fraction Non-luminous (dark) matter: 25%

Natural explanation: new stable WeaklyInteractingMassiveParticle[21]

(24)

Classic Dark Matter Signature

Missing transverse energy

carried away by dark matter particles

(25)

Newton’s law

m • ←−r−→ • m Fgrav= GN

m2

r2 GN−1/2 = MPlanck = 1019 GeV Compare with electric force: Fel= e2

r2 =>

effective dimensionless coupling GNm2 or in general GNE2 at energies E

E = mproton => Fgrav

Fel = GNm2proton

e2 ≃ 10−40 => Gravity is very weak ! At what energy gravitation becomes comparable to the other interactions?

MPlanck ≃ 1019 GeV → Planck length: 10−33 cm 1015 × the LHC energy! [21]

(26)

Mass hierarchy problem

Higgs mass: very sensitive to high energy physics

quantum corrections: δmH ∼ scale Λ of new physics/massive particles stability requires adjustment of parameters at very high accuracy to keep the physical mass (mtreeH )2+ δmH2 at the weak scale

Λ = MGUT or MP => fine tuning at 28-32 decimal places ! Why gravity is so weak compared to the other interactions? [32]

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Standard picture: low energy supersymmetry

every particle has a superpartner with spin differ by 1/2 cancel large quantum corrections to the Higgs mass

=> superpartner mass splittings must be not far from MW Advantages:

natural elementary scalars gauge coupling unification[22]

LSP: natural dark matter candidate prediction of light Higgs

rich spectrum of new particles within LHC reach

(28)

Problems of supersymmetry

too many parameters: soft breaking terms supersymmetry breaking mechanism: unknown Standard Model global symmetries are not automatic

conditions on soft terms for suppression of flavor changing processes no satisfactory model of supersymmetric grand unification

higgsino mass problem:

supersymmetric mass parameter but of the order of the soft terms MSSM : already a % - %0 fine-tuning

‘little’ hierarchy problem

(29)

String theory:

Quantum Mechanics + General Relativity point particle → extended objects

• →

particles ≡ string vibrations - quantum gravity

- framework of unification of all interactions - “ultimate” theory: · ultraviolet finite

· no free parameters mass scale(tension): Mstring ↔ size: lstring rigid string : known particles (massless) vibrations : infinity of massive particles

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At what energies strings may be observed?

Are there low energy string predictions testable at LHC ?

(32)

Very different answers depending mainly on the value of the string scale Before 1994: Mstring near MPlanck at ∼ 1018 GeV lstring≃ 10−32 cm

ց

MW

102

MPlanck

1018 GeV

After 1994: Mstring is an arbitrary parameter

High string scale: natural for supersymmetry and unification but no stringy test at LHC

Interesting possibility: Mstring ∼ MW => nullify the hierarchy problem low UV cutoff Λ ≃ Mstring [26]

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Extra dimensions and braneworlds

Consistency of string theory ⇒ 9 spatial dimensions !

=> six new dimensions of space

matter and gauge forces may be localized in less than 9 dimensions

=> our universe on a extended membrane ? [37]

p-brane: extended in p spatial dimensions

p = 0: particle, p = 1: string, p = 2: membrane,. . .

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Extra dimensions

how they escape observation?

finite size R Kaluza and Klein 1920

energy cost to send a signal:

E > R−1compactification scale experimental limits on their size light signal ⇒ E >∼ 1 TeV

R <∼ 10−16 cm how to detect their existence?

motion in the internal space => mass spectrum in 3d

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How many dimensions ?

(36)

example: - one internal circular dimension - light signal

5

plane waves eipy periodic undery → y + 2πR

=> quantization of internal momenta: p = Rk ; k = 0, 1, 2, . . .

=> 3d: tower of Kaluza Klein particles with masses Mk = k/R p02− ~p2− p52 = 0 => p20− ~p2= p52= Rk22

E >> R−1: emission of many massive photons

⇔ propagation in the internal space

(37)

Our universe on a membrane

Two types of new dimensions:

• longitudinal: along the membrane

• transverse: “hidden” dimensions only gravitational signal => R<

∼ 1 mm !

(38)

Adelberger et al. ’06

R<∼ 45 µm at 95% CL

• dark-energy length scale ≈ 85µm [52]

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Low scale gravity

Extra large ⊥ dimensions can explain the apparent weakness of gravity total force = observed force × volume ⊥

↑ ↑ ↑

GN = GN × V

GN = M−(2+n) : (4 + n)-dim gravitational constant

n dimensions of size R

=> V= Rn

total force ≃ O(1) at 1 TeV => M≃ 1 TeV

n = 1 : R≃ 108 km excluded

n = 2 : R≃ 0.1 mm (10−12 GeV)

possible n = 6 : R≃ 10−13 mm (10−2GeV)

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String theory realization: D-brane world

• gravity: closed strings propagating in 10 dims

• gauge interactions: open strings with their ends attached on D-branes Dimensions of finite size: n transverse 6 −n parallel

calculability => Rk ≃ lstring ; R arbitrary

GN =gs2ls2+n gs : string coupling (≃ gauge coupling for D-branes) Ms ∼ 1 TeV => Rn = 1032lsn

distances > R : gravity 3d but for < R : gravity (3+n)d[42]

strong gravity at 10−16 cm ↔ 103 GeV

1030× stronger than thought previously! [43]

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Braneworld

2 types of compact extra dimensions: • parallel (dk): <∼ 10−16 cm (TeV)[45]

• transverse (⊥): <∼ 0.1 mm (meV)[51]

open string

closed string

Extra dimension(s) perp. to the brane

Minkowski 3+1 dimensions

d extra dimensions||

p=3+d -dimensional brane//

3-dimensional brane

(42)

Gravity modification at submillimeter distances

Newton’s law: force decreases with area

3d: force ∼ 1/r2 (3+n)d: force ∼ 1/r2+n

observable forn = 2: 1/r4 with r << .1 mm

(43)

Gravitational radiation in the bulk = > missing energy

P

P γ or jet

present LHC bounds: M>

∼ 3 − 5 TeV

Collider bounds on R in mm

n= 2 n= 4 n= 6

LEP 2 4.8 × 10−1 1.9 × 10−8 6.8 × 10−11 Tevatron 5.5 × 10−1 1.4 × 10−8 4.1 × 10−11 LHC 4.5 × 10−3 5.6 × 10−10 2.7 × 10−12

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Black hole production

Giddings-Thomas, Dimopoulos-Landsberg ’01

String-size black hole energy threshold : MBH≃ Ms/gs2

Horowitz-Polchinski ’96, Meade-Randall ’07

weakly coupled theory => strong gravity effects occur much above Ms, M

gs ∼ 0.1 (gauge coupling) => MBH∼ 100Ms

Comparison with Regge excitations : Mj = Ms√ j =>

production of j ∼ 1/gs4 ∼ 104 string states before reach MBH

(45)

Other accelerator signatures

Large TeV dimensions seen by SM gauge interactions

=> KK resonances of SM gauge bosons[41] I.A. ’90

Mn2=M02+ k2

R2 ; k = ±1, ±2, . . . string physics and possible strong gravity effects

Massive string vibrations => e.g. resonances in dijet distribution [49]

Mj2 =M02+ Ms2j ; maximal spin: j + 1

higher spin excitations of quarks and gluons with strong interactions Anchordoqui-Goldberg-L¨ust-Nawata-Taylor-Stieberger ’08 extra U(1)’s and anomaly induced terms[50]

masses suppressed by a loop factor from Ms

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Localized fermions (on brane intersections)

=> single production of KK modes I.A.-Benakli ’94

f

f _

n_ R

• strong bounds indirect effects: R−1>

∼ 4 TeV

• new resonances [48]

Otherwise KK momentum conservation

=> pair production of KK modes (universal dims)

n_ R

-n_

R f

f _

• weak bounds R−1>∼ 500 GeV

• no resonances

• lightest KK stable ⇒ dark matter candidate Servant-Tait ’02

(47)

Standard Model on D-branes

I.A.-Kiritsis-Rizos-Tomaras ’02

• U(1)4⇒ hypercharge + global symmetries

• νR in the bulk ⇒ small neutrino masses

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R−1= 4 TeV[46] I.A.-Benakli-Quiros ’94, ’99

1500 3000 4500 6000 7500

Dilepton mass 10-6

10-5 10-4 10-3 10-2 10-1 100

Events / GeV

γ + Z γ Z

(49)

Universal deviation from Standard Model in jet distribution

Ms = 2 TeV

Width = 15-150 GeV

Anchordoqui-Goldberg- ust-Nawata-Taylor- Stieberger ’08 [45]

present LHC limits (2010 data): Ms>∼ 5 TeV

(50)

Extra U(1)’s and anomaly induced terms

masses suppressed by a loop factor

usually associated to known global symmetries of the SM (anomalous or not) such as (combinations of)

Baryon and Lepton number, or PQ symmetry

in general they become massive due to anomalies but global symmetries remain in perturbation - Baryon number => proton stability

- Lepton number => protect small neutrino masses

(51)

Standard Model on D-branes

R

L

LL

ER

QL

U , D

R R

W

gluon

Sp(1) U(1)

U(1) U(3)

1-Leptonic 3-Baryonic

2-Left 1-Right

≡ SU(2)

U(1)3 ⇒ hypercharge + B, L global

(52)

microgravity experiments

change of Newton’s law at short distances[38]

detectable only in the case of two large extra dimensions new short range forces

light scalars and gauge fields if SUSY in the bulk

or broken by the compactification on the brane I.A.-Dimopoulos-Dvali ’98, I.A.-Benakli-Maillard-Laugier ’02 such as radion and lepton number

volume suppressed mass: (TeV)2/MP ∼ 10−4 eV → mm range can be experimentally tested for any number of extra dimensions - Light U(1) gauge bosons: no derivative couplings

=> for the same mass much stronger than gravity: >∼ 106

(53)

Experimental limits on short distance forces

V(r ) = −G m1rm2 1 + αe−r /λ

Radion ⇒ M >∼ 6 TeV 95% CL Adelberger et al. ’06

(54)

improved bounds in the range 5-15 µm

Geraci-Smullin-Weld-Chiaverini-Kapitulnik ’08

10-2 10-1 100 101 102 103 104 105 106 107 108 109 1010

Excluded by experiment

Lamoreaux

U.Colorado Stanford 2

Stanford 1

U.Washington 2 gauged

B#

Yukawa messengers dilaton

KK gravitons

strange modulus gluon modulus

heavy q moduli

Stanford 3 α

U.Washington 1

(55)

Cantilever resonance (f0): ~300 Hz Drive frequency(f0/3): ~100Hz

motion

Cantilever resonance (f0): ~300 Hz Drive frequency(f0/3): ~100Hz

motion

z

x y

Piezo actuator (+/- 120 µm at f /3)0 Fiber

Drive mass T est mass

Cantilever

Silicon nitride shield (cutaway)

(56)

improved bounds from Casimir effect in the nm range

Decca-Fischbach et al ’07, ’08

(57)
(58)

Neutron scattering:

bounds in the range

∼ 1pm - 1nm

Nesvizhevsky-Pignol- Protasov ’07

|2log|g

-26 -24 -22 -20 -18 -16 -14 -12 -10 -8

Random potential model

Comparing forward and backward scattering Comparing forward scattering and total X-section Asymmetry of scattering on noble gases

EXCLUDED REGION antiprotonic atoms

Ederth

Mohideen

Purdue Unseen extra UCN gravitational level

gauge boson in extra dimensions Electroweak scale new boson

LIMITS ON EXTRA YUKAWA FORCE

mass [eV]

1

2 10

3 10

4 10

5 10 10

(59)

Conclusions

Confirmation of the Higgs scalar discovery at the LHC : important milestone of the LHC research program

LHC and Particle physics in a new era with possible new discoveries unveiling the fundamental laws of Nature

Future plans to explore the 10-100 TeV energy frontier

(60)

The LHC timeline LS1 Machine Consolidation

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LS2 Machine upgrades for high Luminosity

•  Collimation

•  Cryogenics

•  Injector upgrade for high intensity (lower emittance)

•  Phase I for ATLAS : Pixel upgrade, FTK, and new small wheel

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LS3 Machine upgrades for high Luminosity

•  Upgrade interaction region

•  Crab cavities?

•  Phase II: full replacement of tracker, new trigger scheme (add L0), readout electronics.

Europe’s top priority should be the exploitation of the full potential of the LHC, including the high-luminosity upgrade of the machine and detectors with a view to collecting ten times more data than in the initial design, by around 2030.

(61)

Future accelerators

ILC project

The future of LHC

(62)
(63)
(64)
(65)
(66)

VHE-LHC: location and size

A circumference of 100 km is being considered for cost-benefit reasons

(67)

This Master program, organized jointly by École Polytechnique (ParisTech) and ETH Zurich, will offer a coherent education in theoretical and experimental High Energy Physics.

2 year program (120 ECTS) 1 year in each institution CONTACTS:

Academic board:

Ignatios Antoniadis (EP Paris and CERN) Jean-Claude Brient (EP Paris) Günther Dissertori (ETH Zurich) Matthias Gaberdiel (ETH Zurich) Master’s administration offices:

master-hep@phys.ethz.ch masters@polytechnique.fr

ÉCOLE POLYTECHNIQUE - ETH Zurich

Particle & Astro-particle Physics

h e p . p o l y t e c h n i q u e . e d u

Quantum Grav

ity & String Theory

Strong & Electroweak Interactions

Theo retic

al &

Observation al Cosmology LHC P

hysics, Supersymmetry & Unifi cation Experimental methods & General Relativity

HOST INSTITUTIONS:

ETH Zurich  - www.ethz.ch ÉCOLE POLYTECHNIQUE - www.polytechnique.edu

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