Particle Physics: an outlook - HEPHY: Startseite · Particle Physics: an outlook. The ’Four-fold way’ of Particle Physics . Issues outside the Standard Model. Neutrino masses.

Particle Physics: an outlook

The ’Four-fold way’ of Particle Physics Issues outside the Standard Model

Neutrino massesSupersymmetryDark MatterMini-Black holes Extra DimensionsAre the natural constants constant ?

1

…Major Open Questions in Particle Physics

• How do leptons and quarks acquire their masses ? -> LHC

• A more complex World: are there higher symmetries ? -> LHC; Astroparticle Physics; Precision Experiments

• What is the nature of ‘Dark Matter’ ? -> LHC; Astroparticle Physics; Precision Experiments

• What are the properties of the ‘Primordial Matter’ ? -> LHC; FAIR

• Matter-Antimatter Asymmetry-> Belle; LHC; FAIR; Astroparticle Physics; Precision experiments

• Are there extra spatial dimensions ? -> LHC; Precision Experiments

• Are the Natural Constants constant ? -> Precision experiments

• The Unexpected -> Accelerators; Astroparticle Physics; Precision Experiments

2

The Experimental Strategy

• This is a vast program for (more than) the next ten years

• This program needs a multi-prong approach - the ‘Fourfold Way’ because- certain questions need to be viewed from different perspectives- certain questions need to be addressed in different energy

regions- no single approach is adequate to answer all these questions

• Plan to show examples of the synergy and complementarity which can be achieved with these diverse approaches- Will emphasize Austrian programmes

3

The Fourfold Way of Experimental Particle Physics

4

New physics signals from Cosmic Accelerators: Astro-particle physicsLand- and satellite-based observation

Fundamentaltopics in

Particle physics

Ultra-precision experiments in ‘laboratory’Direct and indirect observations

Precision tests at ‘Low Energy’ Accelerators(AD, JPARC, FAIR)New physics through virtual phenomena

Experimentation at High Energy Colliders (LHC, BELLE, FAIR)New physics in energy range of accelerators

HEPHY Activities

• Research with CMS- SM Physics (Quarkonia): precision tests of QCD; benchmarks for

Quark-Gluon Plasma studies- Central Topic: SUSY Physics; in collaboration with HEPHY SUSY

Phenomenologists• Research with Belle and Belle II at KEK (Japan)

- Precision measurements of CKM Matrix Elements- Leadership of Belle CKM Analysis group - Global responsibility for Si-Tracker for Belle II- High sensitivity for BSM with Belle II (LHC complementarity)

• Participation in Detector Group for International Linear Collider• Algorithm Group: development of new analysis algorithms

- Responsible for Vertex, Tracking, Alignment algorithms in CMS- Development of new vertexing and tracking algorithm for Belle2

HEPHY Activities

• Semiconductor Detector and Electronics- Major contributions (~ 20%) to CMS Tracker- Global responsibility for CMS Trigger (development, construction,

operation)- Global responsibility for Belle2 Tracker and readout electronics

• SUSY and QCD Phenomenology• GRID-Rechenzentrum ‘Tier 2’:

- Developed together with Univ. Innsbruck- Responsibility of operation; contractual obligation to CMS collaboration- Contribution to Organisation and Implementation of Austrian National

GRID Organisation- Collaboration with other research units

- Medizin-Universität (Optimisation of cancer therapy radiation protocols using simulations programs developed for particle physics

Neutrinos

7

Pauli: light (mass=0) neutral particle to explain the continuous electron spectrum in β-decay

However, assumption of zero mass was put into question, originally by Pontecorvo, considering the possibility of neutrino flavor oscillations (transformation of e.g. electron neutrino into muon neutrino

Davis-Bahcall Solar neutrino experiment in Homestake mine

8

Solar neutrino (νe) productionprocesses

Solar neutrino (νe) spectrum

Davis was leading the experimental effort, Bahcall was leading the Theoretical effort to calculate the spectrum and rate.. There followed a 30 year struggle between experiment and theory

Homestake experiment (1970-1994)

9

Located in underground mine to shield against cosmic rays; tank filled with 400 000l ofperchlorethylene; neutrino induced transformation of Cl into Ar; (basically: n+νe -> p+ e) needed to detect electron emission from Ar; approximately 0.5 Ar atoms produced/ day and0.1 atoms detected... The 30-year issue: measured rate approximately 30% of calculated rate..Who is wrong ? Surprise: both (Bahcall and Davis) were rightBahcall(1996): solution of Solar Neutrino problem requires New Physics!

This reaction has a threshold of 0.8 MeV and hence is not sensitive to the pp-reaction

Neutrino Oscillations

• Old suggestion, originally put forward by B. Pontecorvo, analogous to K0- K0 bar oscillations

• Basic idea: neutrinos created as flavor eigenstates, but propagate through space as a superposition of mass eigenstates- Weak interaction eigenstates νe, νμ, ντ are expressed

combinations of mass eigenstates ν1, ν2, ν3

• Simplified consideration for two neutrino flavors νe and νμ- Each will be a linear combination of two mass eigenstates, given

by unitary transformaion with a specific mixing angle θ

- With the corresponding wavefunctions

10

−

=

2

1

cossinsincos

νν

θθθθ

νν

µ

e

θνθνν

θνθνν

µ cossin

sincos

21

21

+−=

+=e

Neutrino oscillations

• The mass eigenstates propagate in space: x...distance from origin of neutrino, Ei , pi... energy, momenta of mass eigenstates; solve time-dependent Schrödinger equation

• With mi << Ei one obtains the time evolution and thethe probabilities for (dis)appearance after time t

• Probability depends on two parameters, to be determined by experiment:- mixing angle θ- Difference of (mass)2 of mass eigenstates

11

[ ][ ])(exp)0()(

)(exp)0()(

2222

1111

xptiEt

xptiEt

+−=

+−=

νν

νν

∆==→

tEmtP ee 4

sin2sin)()(2

222θνννν µµ

21

22

2 mmm −=∆

Generalization for three neutrino flavors

• Unitary matrix with three mixing angles and one CP- violating phase δ

12

Atmospheric neutrinos

13

Cosmic ray proton initiates particle interaction and shower in atmosphere

p + Nucleon -> π’s +X

π -> μ + νμ

μ -> e + νμ + νe

Expect for every νe 2 νμ ‘s

Confirmed by Monte Carlo calculations

Experimental Observations ofatmospheric neutrinos: discrepancy, again!

14

Moral of this story: research is like high-performance sports: one has to work very hard and sometimes one misses the goal, But: when you succeed, it is Paradise!

Neutrino flux and direction in Superkamiokande

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‘Up- going’ neutrinos coming from opposite side of earth (-1< cosθ < -0.2)‘Down-going’ neutrinos coming from above detector (0.2 < cosθ < 1)

Kamiokande and Superkamiokande

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Tank filled with ultra-pure water (total volume: 50 000 tons); walls were covered with 11 000, specially developed, Photomultipliers (50 cm dia.)Detection of electrons from νe + N -> e + X, detections of muons from νμ + N -> μ + X via Cherenkov radiation

Discrimination between electrons and muons

17

Multiple scattering is stronger for the lighter electrons compared to muons -> the Cherenkov ring reflecting the emission of Cherenkov light is thereforemore diffuse for electrons

Muon event

18C. Wulz

Electron event

19C. Wulz

Muon and electron events as function of zenith angle

• Observed distribution vs zenith angle- Over the distance probed, electron neutrinos do not show

oscillations; muon neutrinos oscillate, consistent with maximal mixing

20

Perkins Fig 9.10, p. 209

Nobel prize for Davis andKoshiba (Superkamiokande)in 2002

Δm2 versus sin22θ for two flavor oscillations

• Summary of various measurements on neutrino oscillations; shaded areas of solar and atmospheric data show regions in which the parameters must lie

21

Perkins Fig 9.6, p. 290

Best fits and contours forSuperkamiokande

22C. Wulz

CERN-Gran Sasso Neutrino beam

23

Aims at tau neutrino appearance observation

Origin of Neutrino masses:indication of physics beyond SM (BSM)?

• Several explanations are being discussed• One of the most popular suggestions:

- there exists a very heavy right-handed neutrino- it mixes with the SM left-handed neutrinos, inducing a very small

mass, inversely proportional to the mass of the hypothetical very heavy right-handed neutrino

• This adds a new mass scale, unrelated to the mass scales of the SM -> hint of BSM- physics

• This mechanism could also explain the mater-antimatter asymmetry through leptogenesis

24

Look for new Symmetries:Is our world more complex, ‘supersymmetric’?

• Such a world would solve several problems...• Would double the number of particles.. .not so nice• New world is related to the rotation properties (‘spin’) of the known

particles- 0 ½ ½ 1 1 - Higgs Lepton Quark Gluon Gauge Bosons - plus supersymmetric partners

- ½ 0 0 ½ ½ - Chargino Slepton Squark Gluino Neutralinos

• Why all this trouble ? Many good reasons…three of them- Would solve the ‚Unnaturalness‘of fine-tuning of higher orders - Would provide unification of the fundamental forces- Would solve a ‚massive‘ problem: the lightest supersymmetric

particle would be a good candidate for dark matter• Austrian physicist Julius Wess was one of the fathers of SUSY 25

Corrections to Higgs Mass Calculation

• Higher order Fermion und Boson corrections to Higgs mass are quadratically divergent: requires ‘unnatural’ compensation ( at level ~ 1013 )

• Naturally avoided, if each Fermion/ Boson has supersymmetric partner

Further reasons for Supersymmetry (SUSY)

SUSY favors Higgs Mass of ~ 150 GeV

SUSY suggest unification of Coupling constants

If SUSY exists, expected to be seen at LHC

• Problem: an unknown parameter space to be explored -> HEPHY is developingmodel-independent analysis strategy

• Ultimate aim is to reconstruct thesecomplex decay chains

• Lightest SUSY particle: dark matter candidatebut would need independent confirmationfrom direct and indirect observation

• If SUSY exists, it will show up inmany different ways: decay of particles,e.g. neutron, B- mesons -> need to look in many different systems

28

Looking for Supersymmetry (SUSY): the Vienna/ HEPHY approach

Example of SUSY particle decay

Production and decay Reconstruction in CMS

Lightest SUSY particle is stable, however only very weaklyInteracting in Detector -> Signature is ‘Missing Energy’

The mysterious recipe of our Universe

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Astrophysical evidence of Dark Matter

31

Colliding cluster MACSJ0025Observation with Hubble space telescope: “Weak lensing" exposes material distributions

Result of systematic quantitative study • gravitationally as normal matter• only weakly interacting

HESS: High Energy Spectroscopic System with Innsbruck participation

32

1st observation of CR interactions due to high matter densityfrom a supoernova outside our Galaxy

Novel analysis techniqueAllows improved e/γSeparation -> severeconstraints on intenselydiscussed excess of electrons, reported byATIC collaboration andinterpreted as Dark Matterannihilation

• As far as we know, there was Matter and Antimatterin symmetric amounts in the very early Universe

• This symmetry was broken: fortunately!• Most matter annihilated with antimatter, BUT

- Approximately one matter particle out of 109 survived- All other matter and antimatter particles annihilated into photons

• All visible matter of our Universe is made from these remnants• The study of this symmetry breaking between matter and antimatter

(CP-violation) is a very active area of research • At present: we have only a very incomplete understanding of this live-saving

symmetry breaking mechanism

33

Mystery of Matter-Antimatter Asymmetry

The dedicated Matter-Antimatter ‘Factory’ (B- and Anti- B mesons) at KEK, Japan

34

CP – Violation in the B- antiB- system

35

B0→J/ψK0

B0→J/ψK0

_

Asymmetry= (N-N)/(N+N)

One example: B0 and to B0 have slightly different masses and lifetimes

Very successful program to test our present theory of CP Violation; Theory developed in the early 70’s by Cabbibo, Kobayashi, Maskawa

_

“… As late as 2001, the two particle detectors BaBar at Stanford, USA and Belle at Tsukuba, Japan, both detected broken symmetries independently of each other. The results were exactly as Kobayashi and Maskawa had predicted almost three decades earlier.”

Success breeds success: Belle II in planning stage

• Belle2 with 10 times higher collision rate• Precision tests with sensitivity beyond

Standard Model• Alternative way to access

TeV scale• Example: SUSY Higgs: may

exceed LHC sensitivity!• Final decision: expected

towards end 2009• In Europe: LN Frascati is also

discussing a similar project

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LHC sensitivity

Belle2 sensitivity toSUSY Higgs

Black Holes at LHC ? • In certain quantum gravity theories-> extra spatial dimensions

• Within these theories-> Mini-Black Holes

• If produced, will be observed

• Lifetime and energy to small to get in contact with matter n

• Cosmic radiation more energetic than LHC -> no indication seen of ‘propagation’ of Mini-Black Holes

Extra Spatial Dimensions Revealed at Ultra-Low Energies ?

• String Theories: explored with the motivation to provide a unified description of the four forces

• In many versions of these String Theories: additional (‘extra’) spatial dimensions (e.g. 3+1 dimensions ⇒ 11 D), which are not (yet) observed, because extra dimensions extend only over very small distance (d << 1 mm) -> possibility of mini-black holes at the LHC

• Extra dimensions ⇒ modify gravitational potentials

n …. total number of dimension

or

α … measures strength; λ … characteristic range

• Experiments have checked and are checking for such modifications38

φ gravity ~ G n

r n−2

φ(r) = −G 4mr 1+ α e−r /λ( )

Theoretical motivation, present experimental limits and expected reach

39

Probing with ultra-cold (< 300 neV) neutrons in the earth’s gravitational field (International ‘Forschungsschwerpunkt’

under Atominstitut co-leadership)

40

Quantum Bouncing Ball: study time evolution of quantum mechanical neutron position

41

This quantum behaviour has been observed!

Medium-term plan: resonant excitation of quantum states;develop high-resolution position detectors

develop application of precision spectroscopy tools to measure resonances improve sensitivity and look for deviations from Newton potential

42

( )λαφ /4 1)( r

rm eGr −+−=

Are Natural Constants constant?

• Very active field, theoretically and experimentally• New concept by ERC Prize winner T. Schumm at Atominstitut• Principle

- Build a new Frequency Standar by using a very narrow, very low-energy transition in Thorium 229Th nucleus

- This transition is very sensitive to fine structure constant α

43

Fundamental physics with a nuclear clock:Shifts of fundamental constants?

Fine structure constant:

1371

21 2

00

≈=he

c εα with

c0 : vacuum speed of light (defined)ε0 : permittivity of vacuum (defined)h : Plancks constant („nature“)e : electron charge („nature“)

describes the strength of the electromagnetic interaction

229Th transition is extremely sensitive to changes in αground stateexcited state

E= 7.6 eV+δE

bind

ing

ener

gy ≈

MeV

bind

ing

ener

gy ≈

MeV

the nuclear atomic clock will be a factor 100.000 more sensitive to variations of the fine structure constant than atomic clocks

zero energy

V. V. Flambaum, Phys. Rev. Lett 97, 092502 (2006)

α

α

electromagnetic interaction

−+≈

s

s

q

q

XX

XX

EE δδ

αδαδ 104105

QCD

qq

mX

Λ=

QCD

ss

mXΛ

=with

The low-energy nuclear transition in 229Th:An ideal “clock” transition

NIST F1 Cs fountain

Oscillator Cs Standard Hg+ Ion Clock Sr lattice clock 229-Th clock

Group NIST NIST JILA ATI Vienna ?

Transition frequency 9.2 GHz 1064 THz 430 THz 1800 THz

Natural line width ≈ 0 1.6 Hz 10 mHz ≈ 10 µHz

Actual line width 1 Hz (ToF) 1.6 Hz 300 mHz (laser) < 3 Hz (magn.)

N Oscillators 108 1 4000 1018

Statistical uncertainty 4 x 10-16 2 x 10-17 1 x 10-18 ≤ 10-25

sensitivity to α: 3 x 1010 Hz 3 x 1015 Hz 3 x 1012 Hz 7 x 1018 Hz

229Th in LiCAFcrystal

229Th isomer state

229Th ground state

[ ]63123 +

[ ]63325 +

∆E ≈ 7.6 eVτ ≈ 5 h

The low-energy nuclear transition in 229Thorium

• extremely narrow transition• excellent shielding by electron shell• infinite interrogation time• up to 1020 local oscillators• easy handling (solid state crystal)→ ideal transition for an (atomic) clock

Outlook: Exciting times!

• During the next decade a number of major facilities will become on-line- LHC has started operation: long, rich program ahead- FAIR construction has been started ; operational towards the end of

the decade- Belle II is scheduled for start of research in 2014- Satellite-based FERMI scheduled to operate for the next decade- CTA: new Cherenkov Array Facility very actively discussed- A very diverse program of low energy; ultra-low energy; precision

and ultra-precision experiments is in the construction phase: necessary, crucial, frequently unique approach to some of the most fundamental physics questions

• Austrian scientists are strongly involved in all these programs, frequently in leadership positions

• I hope many of you will share this excitement ! Thank you and all the best for your studies

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Sommersemester 2011

• Ergänzende Lehr-veranstaltungen:• R. Frühwirth: Statistische Methoden der Datenanalyse (VO: 142.340

/ UE: 142.351) M. Jeitler: Astro-Teilchenphysik (VO: 142.094) – im SS 2011.Ch. Schwanda: Data Analysis of Experiments with Particle Detectors (VO: 141.151) – SS 2011.M. Krammer: Projektarbeit Experimentelle Teilchenphysik (PA: 142.039) – im SS 2010 und WS 2011.

• C.W. Fabjan, Projektarbeit aus experimenteller Teilchenphysik• M. Krammer: Grundlagen der Teilchendetektoren• HEPHY Sommerstudenten-Programm: bitte HEPHY WeB-Seite

beachten; ab März 2011• CERN Sommerstudentenprogramm• Diplomarbeiten: alle Dozenten des HEPHY

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Prüfungsfragen zur Teilchenphysik-Vorlesung (Beispiele)

Particle detectors and particle accelerators• Describe the major components of a particle accelerator and their function• What is a cyclotron, a synchro-cyclotron ?• Describe the major components of the LHC; what is luminosity, centre-of-mass energy?• Define the ‘Invariant Mass’ of a two particle system• How is the momentum of a particle measured? Relation between momentum resolution,

momentum, spatial resolution?• What quantity describes the Bethe-Bloch formula? Discuss the principal features• What is the Landau-distribution of the energy loss?• What is a semiconductor tracking detector?• What is a Multiwire Proportional Chamber; a TPC?• Describe methods of particle identification• What is the Cherenkov Effect? What is its use in particle identification?• What is a calorimeter?• Describe the energy measurement of high-energy photons, of high-energy charged pions• What is a Hadron-Calorimeter?• Describe the principal components of the CMS Detector

48

Prüfungsfragen zur Teilchenphysik-Vorlesung (Beispiele)

QED• Discuss the Feynman diagram for Bhabha scattering, for Compton scattering• Describe conceptually the influence of the medium on the effective em coupling constant• What describes the ‘Dirac Equation’? What is its essential new prediction?• Which invariance principle is applied in QED to generate the QED Lagrangian?• What is a key consequence of local gauge invariance?• Discuss generically Feynman rules: vertex contribution, propagator• What does one understand under ‘renormalization’?• What is the Lamb shift? Describe the original measurement• Muon magnetic moment: what is it? How is it measured?

49

Prüfungsfragen zur Teilchenphysik-Vorlesung (Beispiele)

QCD• What is Isospin? what is Isospin invariance ?• For what purpose was the quark concept introduced?• What are quarks? what is the color charge ? why was the color charge introduced ?• What are gluons? What are its properties?• What is ‘confinement’, ‘asymptotic freedom’?• Describe the effect of the medium on the effective strong coupling• Why are free quarks not observed?• What is the Quark-Gluon Plasma?• Which experiments established the physical reality of quarks?• How was the charge distribution of the proton measured? What is a form factor?• How was the charm quark discovered? • What means ‘Deep Inelastic Scattering’?• What key result of ‘Deep Inelastic Scattering’ experiments indicates the presence of quarks

in the nucleon ?• What are the properties of quarks?• What is a “parton momentum distribution’ (structure function) ?• Draw conceptually the momentum distribution of valence quarks

50

Prüfungsfragen zur Teilchenphysik-Vorlesung (Beispiele)

QCD• How do quarks/gluons manifest themselves experimentally?• How is the number of color charges determined experimentally?• What is the ratio R in collisions?• Which is the local invariance principle in QCD?• What is – compared to QED – the new feature in quark/gluon interactions?• Sketch the Q-dependence of the strong coupling constant

51

Prüfungsfragen zur Teilchenphysik-Vorlesung (Beispiele)

Weak/Electroweak interactions• What is a neutrino? Why was it introduced?• What is parity?• What is parity violation? Describe the first experimental observation of parity violation• What is the fundamental reason why parity is maximally violated in WI?• How was the helicity of the neutrino experimentally first measured?• What is CP-violation?• How was C`P-violation discovered?• What is CTP?• What is fundamentally different in weak interactions compared to QED or QCD?• Sketch the Feynman diagram for n-decay, μ-decay• What are ‘neutral currents’? How were they discovered?• Discuss the coupling of quarks to • What is fundamentally different in Λ-decay compared to n-decay?• What is the Cabbibo mixing angle, the GIM mechanism ?• What is the CKM formalism? Why was it introduced?• What was Glashow’s key new idea in unifying the electromagnetic and weak interactions?

52

Prüfungsfragen zur Teilchenphysik-Vorlesung (Beispiele)

Weak/Electroweak interactions• What are the key steps in arriving at the ‘Higgs mechanism’?• Why was the ‘Higgs mechanism’ introduced?• What is ‘Spontaneous symmetry breaking’?• Describe the basic accelerators and experimental developments leading to the W- and Z-

discovery• What are the experimental signatures of W- and Z-Bosons?• How was the number of total neutrinos measured at LEP?• What is experimentally known about the Higgs?• What is the Solar Neutrino Puzzle?• How were neutrino oscillations inferred from atmospheric neutrinos?• What is Supersymmetry?• Explain two possible consequences of Supersymmetry • What are ‘Extra dimensions’? Explain the role of ultra-cold neutrons in the study of extra

dimensions

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