Dezso Horváth˝ horvath@rmki.kfki.hu KFKI Research Institute for...

transcript

Matter and AntimatterDezso Horváth

horvath@rmki.kfki.hu

KFKI Research Institute for Particle and Nuclear Physics, Budapestand Institute for Nuclear Research, Debrecen

Dezso Horváth: Matter and Antimatter Symmetry Festival 2009 Budapest, 31 July — 05 August 2009 – p. 1

Outline

Symmetries in the Standard Model

Antiparticles and CPT Invariance

Antimatter in the Universe?

Testing CPT Symmetry

Supersymmetry?

Search for Supersymmetry at LHC

Symmetries

Deeper microstructure ⇒ greater role of symmetries

Field theory: Noether’s theoremContinuous symmetry ⇒ conserving quantity

Spatial displacement ⇒ momentumTime displacement ⇒ energyRotation ⇒ angular momentumGauge invariance ⇒ charge (electric, color, fermion)

Popular journal of Fermilab and SLAC:symmetry — dimensions of particle physics

The Zoo of the Standard Model

colored quarks ⇒ colorless composite hadronshadrons = mesons (qq) + baryons (qqq)

Nucleons (I = 12): p = (uud) n = (udd) p = (uud)

Interactions

Standard Model:Free Dirac (point-like) fermion

+ local U(1)⊗SU(2) symmetry⇒ electroweak interaction (γ, Z, W±)

+ local SU(3) symmetry⇒ strong interaction (8 gluons)

+ Higgs field with spontaneous symmetry breaking⇒ masses, convergence (+ Higgs boson)

Fundamental job of particle physics:study symmetries

Father of (quantum) field theory:Steven Weinberg

Glory Road of Standard Model

Summer 2009 status

Includes hundreds ofmeasurements of all experiments

|Expt – theory|expt. uncertainty

Slightly deviating quantitychanges from year to year

Now it is forward-backwardasymmetry of

e+e− → Z → bb

LEP Electroweak Working Group:

http://lepewwg.web.cern.ch/

Spontaneous symmetry breaking⇒ mass

Freefermion

Higgsboson

David J. Miller and CERN: http://www.hep.ucl.ac.uk/∼djm/higgsa.html

Where is the Higgs-boson?By-product of spontaneous symmetry breaking of the SM

Most wanted particle of physics as

the only missing piece of the Standard Model.

Experimentally not (yet?) observed,

LEP: M(H) > 114.4 GeV

“It was in 1972 ...

that my life as a boson really began”

Peter Higgs:

My Life as a Boson: The Story of “The Higgs”,

Int. J. Mod. Phys. A 17 Suppl. (2002) 86-88.

Fitting the mass of the Higgs boson

10030 300

mH [GeV]

∆χ2

Excluded Preliminary

∆αhad =∆α(5)

0.02758±0.00035

0.02749±0.00012

incl. low Q2 data

Theory uncertaintyMarch 2009 mLimit = 163 GeV

Summer 2009 status

Sensitivityof SM parameters

to Higgs mass

114< MH < 163GeV(95 % confidence)

LEP Electroweak Working Group:http://lepewwg.web.cern.ch/LEPEWWG/

CPT Invariance

Basic assumption of field theory:CPT|p(r, t)> ∼ |p(−r,−t)> ∼ |p(r, t)>

meaning free antiparticle∼

particle going backwards in space and time.

Giving up CPT one has to give up:

locality of interactions ⇒ causality, or

unitarity ⇒ conservation of matter, information,

... or Lorentz invariance

Motivation to doubt:

Asymmetric Universe: no antimatter galaxies

Antimatter in the Universe?

Is it possible to explain its lack without assuming CPTviolation?

YES: Theory of Andrei Sakharov, 1967Baryogenesis (the prevalence of baryons against

antibaryons) in the Universe can be explained if the three(Sakharov) conditions are fulfilled:

violation of baryon number conservation

violation of CP-symmetry

faster expansion than baryon-antibaryon production ⇒low chance for subsequent annihilation.

CP-violation observed, baryon number violation not.Experimental test: LHCb at CERN

Accelerators at CERNUntil 2000 From 2008

LHC: the Largest Microscope

LHC: the dipole magnets

1232 superconducting dipoles (before installation)(L = 15 m, M = 35 t, T = 1.9 K, B = 8.3 T)

LHC: magnets in tunnel

The LHCb experiment at CERN

CPT Invariance: violation?Theoreticians in general: CPT is NOT violated

CPT-violating theories:(Alan Kostelecký, F.R. Klinkhamer, N.E. Mavromatos et al)

Standard Model valid up to Planck scale (∼ 1019 GeV).Above Planck scale new physics ⇒Lorentz violation possible

Quantum gravity: fluctuations ⇒ Lorentz violationloss of information in black holes ⇒ unitarity violation

Motivation for testing CPT at low energy

Quantitative expression of Lorentz and CPT invarianceneeds violating theory

low-energy tests can limit possible high energyviolation

How to testCPT?

Particle = – antiparticle ?

|m(K0)−m(K0)|/m(average) < 10−18

proton ∼ antiproton? (compare m, q,~µ)

hydrogen ∼ antihydrogen (antiproton+positron)?(2S−1S transition!)

Antihydrogen (antiproton+positron)

2-photon 2S−1S transition:

Slow transition ⇒ narrow lineTwo counter-propagating photons ⇒ Doppler-free

Accelerators at CERNUntil 2000 From 2008

The Antiproton Decelerator at CERNis built to test CPT invariance

Three experiments test CPT:

ATRAP: q(p)/m(p) ↔ q(p)/m(p)

H(2S−1S) ↔ H(2S−1S)

ATHENA ⇒ ALPHA:

H(2S−1S) ↔ H(2S−1S)

ASACUSA: q(p)2m(p) ↔ q(p)2m(p)

µℓ(p) ↔ µℓ(p)

H ↔ H HF structure

RED: done, GREEN: plannedc©Ryugo S. Hayano

Lots of H produced, spectroscopy

is aheadHayano, Hori, Horváth and Widmann: Repts. Prog. Phys.70 (2007) 1995-2065.

Lost symmetries?“.. the fundamental equations of physics have more symmetry

than the actual physical world does”Frank Wilczek: In search of symmetry lost, Nature 433 (2005) 239

“Accidental symmetries” Steven Weinberg

CPT invariance: fundamental, absolute, no violationSU(3) gauge invariance

conserves color chargegives rise to strong interactionsno violation

U(1)×SU(2) gauge invariancespontaneously broken by Higgs fieldgives rise to electroweak interactionproduces Higgs boson

What else?

Supersymmetry (SUSY): motivationTheoretical problems of Standard Model:

Naturalness (hierarchy): Mass of Higgs bosonquadratically diverges due to radiative corrections.Eliminated if fermions and bosons exist in pairs.

Dark matter and energy give dominant energy ofUniverse. What is DM that we observe its gravity only?

Gravity: does not fit in system of gauge interactions(strong, electromagnetic, weak)

Convergence of interactions: in SM the three gaugecouplings converge at ∼ 1016 GeV but do not meet

All these would be solved by a universalfermion ⇔ boson supersymmetry.

Supersymmetry: partner particles

Charges (electric, color, fermion) identical

SUSY partners of fermionsLeptons (S= 1

2) scalar leptons (S= 0)

e, µ, τ e, µ, τνe, νµ, ντ νe, νµ, ντ

Quarks (S= 12) scalar quarks (S= 0)

u, d, c, s, t, b u, d, c, s, t, b

Antiparticle ↔ antipartner

XL, XR ↔ X1, X2

SUSY partners of bosons

Elementary boson spin SUSY partner spinphoton: γ 1 photino: γ 1

weak bosons: 1 zino: Z 12

Z, W+, W− 1 wino: W+, W− 12

gluons: g1, ... g8 1 8 gluinos: g1, ... g812

Higgs fields 0 higgsinos 12

H01, H0

2, H+1 , H−

2 H01, H0

2, H+1 , H−

graviton 2 gravitino 32

Two Higgs doublets ⇒ 5 Higgs bosons: h, H, A, H+, H−

Supersymmetry?

Supersymmetry is obviously broken:no such particles,

or maybe with much larger masses

What is a broken symmetry good for?

Higgs mechanism:symmetry violating field ⇒ masses, renormalisation

Higgs field violates an existing symmetrym

SUSY introduces a non-existing one

All this for a rational, cosistent theory

Unification of gauge interactions

Standard Model:

Gauge couplings get close athigh energies

Convergence at ∼ 1016 GeV.Extra particles ⇒ corrections

Frank Wilczek: Nature 433 (2005) 239

Supersymmetry: + and−

naturalness of theory

cold dark matter of the Universe (23 %) = LSP

unification of interactions

includes gravitation

−Mechanism of SUSY breaking ??

Many different models

Many new parameters

Not seen below m∼ 100GeV

SUSY is already 50% discovered!!

We see half of all SUSY particles(except the Higgs-boson :-)...)

Search for SUSY particles

Creation in pairs, decay to ordinary and SUSY particles

Properties depend on models and parameters

Lightest SUSY particle (LSP) unobservable⇒ missing energy observed

Which one is LSP? Model dependent.

SUSY (and Higgs) search at CERN:Large Electron-Positron collider (LEP), 1989 – 2000;

Large Hadron Collider (LHC), 2010 –

The Large Hadron Collider at CERN

Search for SUSY particles at LEPDifficult: hard to distinguish from SM reactions.

Scalar lepton formation e+e− → ℓ+ℓ−

Decay e.g. ℓ±→χ01ℓ

±, model-dependent cross sections

Look for e+e−→ ℓ+ℓ− + missing energy

Main background: e+e− → W+W−→ ℓ+νℓ−ν

LEP result (ALEPH + DELPHI + L3 + OPAL):

No supersymmetric particle below m∼ 90−100GeV(kinematic limit: LEP worked up to 200 GeV)

Statistical analysis ⇒ excluded parameter regions

Compact Muon Solenoid (CMS)

The CMS detector of LHC(Compact Muon Solenoid)

Weight: 12500 tons, 2∗ more iron, than in Eiffel tower

> 2000participants

Largest (superconducting) solenoid on Earth:13 m long, 5.8 m inner diameter , B = 4 Tesla

Proton bunches collide at 40 MHz (25 ns!)(uud + uud) ⇒ many hadrons

Each event contains 10-15 p-p interactions

Event filter: ≈ 4000PC, 500 GBit/secEvent storage: ≈ 10 PB data, 10 PB MC per yearData handling: LHC Computing Grid (> 100sites)

Signal: lepton or jet orthogonal to beam,Larger mass easier to identify

Simulated H→ ZZ → eeqq at CMS

SUSY search with CMSSignal: Particles of SUSY pair → fermions + lighter SUSY

→ ... → fermions + LSP

Fermion cascade with missing transverse momentum

g → bb → χ02 b b→ ℓ+ ℓ− b b→ χ0

1 ℓ+ ℓ− b b

Measurements for all parameter values of all models??

Collaboration with theorists:check benchmark points in parameter space

Given model and parameters ⇒quantitative prediction of SUSY properties

and reaction probabilities ⇒can be tested experimentally

Angels and Demons at CERNNovel by Dan Brown, film with Tom Hanks

Terrorists steal 1 g of antimatter from a secret CERN lab to destroy theVatican, Hanks stops them (of course)

CERN offered location, but film was taken in Los AngelesCERN: home page, special exhibition, talks

True: LHC underground, antimatter produced (few atoms)False: No secret lab, 1 g antimatter in 109 years

LHC: the Good, the Bad and the Ugly

GoodEnormous discovery potential:Various reactions at very high

energies,huge luminosity.

BadTerrible background,

interesting events happenat probability 10−6−10−3

UglyAny interesting event is

accompanied by 10–20 p-pcollisions giving high combinatorial

backgrounds.

SUMMARY

No Higgs boson, nor supersymmetry found at LEPLHC starts in 2009 with low luminosity, at 10 TeV

We hope for discoveries from 2010Even 10 TeV collision energy is enough for discoveries:

Higgs boson(s), SUSY particles

For precise studies one needs e+e− collider:International Linear Collider (ILC)

LHC design started before LEP constructionILC plans are developing worldwide

Thanks for your attention

Dezso Horváth˝ horvath@rmki.kfki.hu KFKI Research Institute for...

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