Welcome/Introduction to RAL (STFC)

Welcome/Introduction to RAL (STFC)Welcome/Introduction to RAL (STFC)

Norman McCubbin

Director of Particle Physics

Graduate Lecture. NMcC Oct 20102

• ~80 people in Particle Physics Department (PPD), ~60 have PhDs, plus engineering, instrumentation, accelerator, and computing in other parts of the laboratories.

• In many respects we are just like a large university PP department (eg Oxford), but no requirement for undergraduate teaching (though a few do some), and a relatively small number of PhD students for a department of this size.

• We provide an ‘interface’ for the whole PP UK community to specialist skills in other RAL/STFC departments:

– Technology: electronics, mechanical engineering;– Computing: the UK Tier-1 is here, and we are part of the South Grid Tier-2

consortium;– Accelerator R&D: ASTEC, which works closely with the Cockcroft and

Adams Institutes;– Project management and administration: e.g financial tendering

• RAL site has been, and is, undergoing massive change: much more building over last 5 years than in previous 25…. : Diamond, ISIS Target Station 2, new hostel, new main gate, new computer building, new research building,….

• All this is part of transformation to Harwell Science and Innovation Campus (HSIC).

Particle Physics DepartmentParticle Physics Department


Current projects in PPDCurrent projects in PPD

Project Approx. FTE

Funding Located at Programme 2010-2012

ATLAS 18 STFC CERN M&O, analysis, tracker upgrade

CMS 11 STFC CERN M&O, analysis, upgrade

LHCb 5 STFC CERN M&O, analysis, upgrade

Computing 8 STFC, EU RAL Grid software, Tier (1,2,3) support

Neutron EDM 4 STFC ILL Deploy cryo-detector, M&O, analysus

Dark Matter 4 STFC Boulby Laboratory

Zeplin III M&O, analysis; plus management of Boulby facility.

Detector R&D 5 STFC RAL, university collaborators

Developments for future PP experiments, and non-PP applications

Neutrino experiments

6 STFC FermilabJ-PARC

MINOS; T2K

Neutrino accelerator R&D

2 + … STFC(+ EU) RAL MICE; Neutrino Factory design studies; FFAG/EMMA

NExT 3 (joint) STFC/HEFCE RAL + So’ton +

RHUL+Sussex(Virtual) Institute for Phenomenology.

Support 8 STFC RAL, UKLO Programme support for UK community


Programme SupportProgramme Support

• STFC/PPD is an essential pillar of UK particle physics– An amplifier for the national programme – PPD co-located at an institution with powerful engineering and

technology capabilities enables Particle Physics UK to carry out projects that it could not otherwise do. For example clean-room for ATLAS, FE and thermal calculations for CMS, ….

• Especially critical for smaller university groups– PPD is held in high esteem throughout the worldwide PP community,

and we are sought-after collaborators.– We are involved in almost all UK PP projects.

• Provides a significant support role for UK Particle Physics– Annual HEP summer school for all UK students– Management and reporting of budgets– Travel processing, booking and reimbursement– Manage UK Liaison Office (UKLO) at CERN. (Previously also smaller

offices at DESY, SLAC, FNAL)


Some big questions Some big questions

• The Standard Model, which works so well at lower energies, falls apart above a few TeV

– Is there a Higgs boson? Other new particles or forces?


The Large Hadron Collider The Large Hadron Collider ..getting ready....getting ready..

ATLAS tracker at RAL

ATLAS tracker installed June 2007

CMS calorimeter crystal

LHC computing and the Grid

NExTNExT

Phenomenology initiative with

Southampton, RHUL and

Sussex

CMS Half ECAL installed June 2007


The Large Hadron Collider The Large Hadron Collider ..data at last!..data at last!





• What is the cosmic dark matter?– Can we detect it? Is it particles we can make at colliders?


• Direct detection of Dark Matter low rate, small energy deposits

– Very sensitive detectors– Well shielded– Underground to avoid cosmic

rays

1100 m

STFC operates the Boulby underground facility, Palmer Lab.

PPD led ZEPLIN-I and ZEPLIN-II liquid xenon projects. ZEPLIN-II published world class result. ZEPLIN-III running well; beyond Nov 2010?

Palmer Lab also hosts DRIFT, SKY,…Long-term

future of Boulby? Long-term

future of Boulby?

• Being addressed now…• LAGUNA in long-term?






• What is the origin of the matter-antimatter asymmetry in the universe?– See effects in quark decays?


Flavour physicsFlavour physics

• Using decays of particles containing b-quarks to explore the small matter-antimatter asymmetry in quark decays

– BaBar experiment at SLAC (ended 2008) – LHCb experiment at CERN

LHCb cavernLHCb cavernLHCb RICH2 detector

LHCb RICH2 detector

BaBarSimulation109 events/year at RAL

BaBarSimulation109 events/year at RAL


Neutron Electric Dipole MomentNeutron Electric Dipole Moment

• Cryogenic apparatus at ILL in Grenoble

– Sussex, RAL, Oxford, Kure, ILL• Builds on previous successful

experiment– world’s best limit 3 10-26 e cm

• Installation complete and device now cooled to 2K

• Goal is sensitivity of few 10-28 e cm

goal

• A permanent neutron EDM would imply Parity and Time Reversal Violation

• Indirect test of matter-antimatter asymmetry

Complementary to accelerator searches






• What is the origin of the matter-antimatter asymmetry in the universe?– See effects in quark decays?– Neutrinos?


Explore CP violationNeutrino Factory• Build community, international

scoping study, EUROnu design study

• RAL is a credible site

First events seen.

Beam power increasing.

T2K• A strong role in detector and

accelerator development and in physics analysis

• Build up UK neutrino community

MINOS• Operations

and analysis

The Neutrino ProgrammeThe Neutrino Programme

MICE• Demonstrate

muon cooling

Technology demonstration


Room to dream!Room to dream!

• ISIS• ISIS 1MW

upgrade• ESS-class 5MW

spallation source• Neutrino factory• Ultimate

multi-TeV muon collider

Harwell Science and Innovation Campus


Knowledge ExchangeKnowledge Exchange

• Two examples

– The LCFI project spent over £500k in industry (e2v) on collaborative development of novel silicon detectors for the International Linear Collider. Patent application in progress.

– FFAG accelerators, being developed for future neutrino facilities, also have significant promise in hadron/ion therapy applications. EMMA is an FFAG “proof of principle”, and has just circulated (e-)beam. We are part of a joint project (BASROC) to develop this within the UK.

• Future accelerator and detector projects are likely to make significantly greater use of industry to develop equipment – “KE through procurement”

• Our biggest KE impact is probably through our ability to attract and train students and postdocs who go on to careers in other areas


A little bit of physics…A little bit of physics…

17UK-HEP_Forum'10-tsv

Bound states of u,d,s (anti-)quarks

Charm (anti-)quarks

Bottom(anti-)quarks

.. and the Z


The di-muon mass spectrum..The di-muon mass spectrum..

• A significant fraction of the (history of the) Standard Model is directly visible in, or implied by, this mass spectrum:

– it’s a quark “directory”, seen through the quark-antiquark bound states;– We see the Z;– Even the non-resonant continuum is “real physics” – though this is a ‘publicity’ plot,

and I don’t know how much off-line selection has been done: eg it would be possible, in principle to subtract out the contribution from two semi-leptonic decays, but I would be surprised if this has been done yet.

• And the rich range of physics topics include:– ρ/ω interference;– “Quarkonium” structure of excited states for c and b systems;– Narrow width of J/ψ and Υ (and large width of ρ/ω);– Drell-Yan continuum;– And the Z width bears directly on number of (light, non-sterile) neutrinos.

–


J/J/ψψ width (1) width (1)

• J/ψ is by now probably one of the best studied particles in physics. The Beijing e+e- collider (BEPC) has collected ~58 million of them, and studied many rare decays.

• The mass has been measured by the VEPP-4M ring with astonishing precision, using the technique of resonance depolarisation:

MJ/ψ= 3096.917 ± 0.010 ± 0.007 MeV

• The widths are much tougher to measure:

• Γtotal = 93+- 2 keV; Γee = Γµµ = 5.6 +- 0.1 keV • The decay into lepton pairs is (of course) through a virtual photon.

Creation (in fermion-antifermion collision) and decay:


J/J/ψψ width (2) width (2)

• This same process can also give decay into quark-antiquark pairs, observed (of course) as hadronic jets:

• For uubar (via virtual photon) we expect: 3.(2/3)2 Γee = 1.3 Γee = 7.4 keV.

• Do you understand the factors?• So, width into u, d and s pairs via virtual photon: ~7.4+1.9+1.9 = ~11keV.• Total width is 93 keV, so decay is not ALL ELECTROMAGNETIC.• Why not decay involving gluons? Which would presumably give us a

‘strong interaction’ width ~ 100 MeV.• First note that the J/psi cannot just ‘fall apart’ into charmed mesons (Why

not?)• But why not decay via a gluon (analogous to photon diagram)?• Can’t decay via one gluon, because of….• Can’t decay via two gluons because of ….

• CAN decay via three gluons, but this implies (αstrong)6

• ..and THAT’s why the J/ψ is so narrow!


..other vector mesons and SU(2)..other vector mesons and SU(2)

• To finish off, let’s look at leptonic widths of the light vector mesons:– ρ(770): Γee = Γµµ = 7.0 keV– ω(780): Γee = Γµµ = 0.60 keV (actually dimuon mode is not that well measured.)

– Φ(1020): Γee = Γµµ = 1.2 keV• Can we understand the relative magnitudes?• Just as for J/ψ, decay involves coupling to virtual photon.• The φ is ssbar: electric charge factor (-1/3)2

• Both ρ and ω are mixtures of u.ubar and d.dbar, but there’s a factor of ~10 difference in leptonic width…

• The u and d quarks play a special role in the strong interactions because their masses and more importantly the mass difference between them are very small compared to ΛQCD.

• In other words, seen by the strong interaction the u and d are pretty much identical (coloured) objects.

• This gives rise to the valuable (for particle physics) and fundamental (for nuclear physics) concept of strong isospin. Mathematically SU(2) symmetry.


.. SU(2).. SU(2)

• The u and d quarks form strong isospin doublet:

• And combinations of u and d quarks get isospin quantum numbers in a manner that is completely analogous to the usual QM angular momentum rules. And the strong interactions conserve strong isospin.

• Angular momentum coupling gives us things like:

• The ω is an isospin singlet (I=0) and the ρ is I=1 – there are three: ρ+,ρ0,ρ-.

• Assuming (correctly) that ubar has I3=-1/2 and dbar has I3=+1/2 would suggest:• ω=1/√2(u.ubar – d.dbar) and ρ=1/√2(u.ubar + d.dbar) • Giving electric charge factors of (2/3-(-1/3))2/2 for ω and (2/3+(-1/3))2/2 for ρ

d

udu :spaceisospin strong in this doublet'' a form du, theSo 2/1;2/1 and 2/1;2/1

)2/1;2/12/1;2/12/1;2/12/1;2/1(2

10;0

)2/1;2/12/1;2/12/1;2/12/1;2/1(2

10;1


.. SU(2) (contd).. SU(2) (contd)

• Which is indeed a factor ~10….

• BUT THE WRONG WAY ROUND! (predicts Γee for ω > Γee for ρ )

• As is often the case, you have to be just a leeetle careful handling antiparticles!

• It is correct that ubar has I3=-1/2 and dbar has I3=+1/2.

• But it is not correct that the SU(2) rotations on ubar and dbar are IDENTICAL to those on u and d. And that messes up the coupling rules for isospin if you have both quarks and antiquarks.

• Fortunately, there is a neat way out: it turns out that the doublet transforms exactly like

• To see this I’ll mimic the discussion given in Halzen and Martin so you can check it later.

d

u

u

d



• A rotation of π/2 about the ‘2’ axis is where τ2 is the appropriate Pauli spin matrix. Applying this to a doublet gives:

• Now apply the charge conjugation operator, C.

• So

• Which is equivalent to:

and dCduCu

d

u

d

u

01

10

'

'

2/2ie

d

u

d

u

d

u

01

10

'

'

u

d

u

d

01

10'



• So the doublet transforms exactly like

• So, we CAN use standard angular momentum coupling, provided we write

–dbar, whenever we want a dbar quark.• So ω=1/√2(u.ubar – d.(-dbar)) and ρ=1/√2(u.ubar + d.(-dbar)) • And all is well!

d

u

u

d

Welcome/Introduction to RAL (STFC)

Documents

uk communitygraduate

uk tier

particle physics uk

uk pp projects

pp uk community

uk studentsmanagement

fnalgraduate lecture

large university pp