exploiting spin effects to unravel the structure of np at a future lc n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Exploiting spin effects to unravel the structure of NP at a future LC PowerPoint Presentation
Download Presentation
Exploiting spin effects to unravel the structure of NP at a future LC

Loading in 2 Seconds...

play fullscreen
1 / 40

Exploiting spin effects to unravel the structure of NP at a future LC - PowerPoint PPT Presentation


  • 81 Views
  • Uploaded on

Exploiting spin effects to unravel the structure of NP at a future LC. ‘Big’ HEP questions Physics case for polarized beams Requirements to a Linear Collider Requirements to a Z-factory Summary. Gudrid Moortgat -Pick Hamburg University. ‘Big’ questions …and possible answers.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Exploiting spin effects to unravel the structure of NP at a future LC' - domani


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
exploiting spin effects to unravel the structure of np at a future lc

Exploiting spin effects to unravel the structure of NP at a future LC

  • ‘Big’ HEP questions
  • Physics case for polarized beams
  • Requirements to a Linear Collider
  • Requirements to a Z-factory
  • Summary

GudridMoortgat-Pick

Hamburg University

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

big questions and possible answers
‘Big’ questions …and possible answers
  • Shortcomings of the Standard Model
    • Establish electroweak symmetry breaking LC
    • Hierarchy problem?
    • Unification of all interactions?
    • Embedding of gravity in field theory?
    • Baryon asymmetry in Universe?
    • Content of dark matter
    • Neutrino mixing and masses
  • Why is new physics expected at TeVscale?
    • Protect hierarchy between mweak and mplanck
    • Dark matter consistent with sub-TeV scale WIMPs

Higgs mass with respect to large quantum corrections:

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

big questions and possible answers1
‘Big’ questions …and possible answers
  • Shortcomings of the Standard Model
    • Establish electroweak symmetry breaking LC
    • Hierarchy problem? LHC, LC
    • Unification of all interactions? LC
    • Embedding of gravity in field th? cosmo,LHC, LC
    • Baryon asymmetry in Universe? v-, cosmo, LHC, LC
    • Content of dark matter?v-, cosmo, LHC, LC
    • Neutrino mixing and masses v-, cosmo-exp.

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

big questions and possible answers2
‘Big’ questions …and possible answers
  • Shortcomings of the Standard Model
    • Establish electroweak symmetry breaking LC
    • Hierarchy problem? LHC, LC
    • Unification of all interactions? LC
    • Embedding of gravity in field theory? cosmo,LHC, LC
    • Baryon asymmetry in Universe? v-, cosmo, LHC, LC
    • Content of dark matterv-, cosmo, LHC, LC
    • Neutrino mixing and masses v-, cosmo-exp.
  • Goal of a Linear Collider?
    • observe, determine and precisely reveal the structure of the underlying physics model !

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

required features at lhc ilc
Required features at LHC & ILC

LC, today only

LHC, LC: CP e.g.

LC, partially LHC

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

why a linear collider
Characteristics of pp collider

composite particles collide

E(CM) < 2 E(beam)

strong interaction in initial state

`no' polarization applicable

LHC: √s = 14TeV,

used ŝ = x1x2s few TeV

small fraction of events analyzed

multiple triggers

superposition with spectator jets

Large potential for

direct discovery

and of the e +e-(γe, γ γ) collider

Pointlike particles collide

Known E(CM) = 2 E(beam)

well defined initial state

polarized initial e- and e+ beams

ILC: √s = 500 GeV -- 1 TeV, tunable

most events in detector analyzed

no triggers required

clean +fully reconstructable events

Large potential for discovery also via high precision

Why a linear collider?

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

the unique advantage of e e
The unique advantage of e+e-
  • Their clean signatures allow precision measurements
      • Sensitive to the theory at quantum level (i.e. contributions of virtual particles, ‘higher orders’)!
  • Such measurements allow predictions for effects of still undiscovered particles, but whose properties are defined by theory.

Enables powerful discoveries and/or consistency checks and the determination of the underlying structure!

t

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

requirements for such precision frontier
Requirements for such`precision frontier’

ICFA Parameter Group for a future LC:

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

why are polarized beams required
Why are polarized beams required?
  • Please remember: excellent e- polarization ~78% at SLC:
    • led to best measurement of sin2θ=0.23098±0.00026

on basis of L~1030 cm-2s-1

  • Compare with results from unpolarized beams at LEP:
    • sin2θ=0.23221±0.00029 but with L~1031cm-2s-1

See importance and more details later when discussing ‘Z-factory’

  • Comprehensive list of physics examples with polarized beams at a LC: GMP et al., Physics Rept., hep-ph/0507011
    • Only few examples here, has to be weighted wrt LHC expectations!

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

beam polarization at hep colliders
Beam polarization at HEP colliders

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

beams polarization at linear colliders
Beams polarization at linear colliders
  • Polarized e- beams:
    • strained photocathode technologies (SLC, etc. )
    • see talks at PESP@Bonn, W. Hillert
    • expected for the LC P(e-)~80-90%
  • Polarized e+ beams: e+ polarization is an absolute novelty!
    • Expected at ILC P(e+) ~ 60%
    • in RDR baseline already ~30% achievable
      • see talks by A. Schaelicke, K. Laihem
  • Measurement via Compton polarimetry: ΔP/P<0.25% exp.
      • see talks by M. Beckmann, D. Kaefer

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

short overview e sources at ilc
Short overview: e+ sources at ILC

-200m

e+ yield and polarization depends on beam energy and undulator length

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

short overview e sources at ilc1
Short overview: e+ sources at ILC

s

-200m

  • in general: demanding challenges for the e+ source!

e+ yield and polarization depends on beam energy and undulator length

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

physics pol cross sections in general
Physics: pol.cross sections in general

Polarized cross sections can be subdivided in:

σRR, σLL, σRL, σLR are contributions with fully polarized L, R beams.

In case of a vector particle only (LR) and (RL) configurations contribute:

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

effective polarization
Effective polarization
  • Effective polarization:

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

relation between p eff and a lr
Relation between Peffand ALR
  • How are Peffand ALR related?
  • That means:
  • With pure error propagation (and errors uncorrelated), one obtains:
  • With

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

gain in accuracy due to p e
Gain in accuracy due to P(e+)

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

p e sensitive to interaction structure
P(e±) sensitive to interaction structure

Definition: Helicityλ=s * p/|p| ‘projection of spin’

Chirality= handedness is equal to helicity only of m=0!

  • Annihilation channel:

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

complete fixing of initial state via p e
Complete fixing of initial state via P(e+)
  • Scattering channel: direct access to chirality of final state !

from SM processes

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

something new detected at early lhc
Something ‘new’ detected at early LHC
  • Supersymmetry-like signals
    • New physics model with

high predictive power

    • ‘light’ SUSY consis-

tent with precision fits

  • Extra gauge bosons and/or large extra dimensions
    • High precision in indirect searches allow model distinction and couplings determination

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

verify susy properties at ilc
Verify SUSY properties at ILC

in t-channel

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

slepton chiral quantum numbers
Slepton `chiral’ quantum numbers

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

models with extra dimensions
Models with extra dimensions
  • String theory: 10 or 11 dimensions of space-time
    • Extra dimensions ‘compactified’, too small to be detected so far:

To a tightrope walker, the

tightrope is one-dimensional:

he can only move forward or

backward

But to an ant, the rope has an extra dimension: the ant can

travel around the rope as well !

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

searches for extra dimensions
Searches for extra dimensions

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

extra dimensions
Extra dimensions

Distinction between SM and different models of extra dimensions

  • Detect and determine new kind of physics even in the multi-TeV range
  • Transversely-polarized beams require P(e-) and P(e+) !

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

polarimetry requirements
Polarimetry requirements
  • SLC experience: measured ΔP/P=0.5%
    • Compton scattered e- measured in magnetic spectrometer
  • Goal at ILC: measure ΔP/P≤0.25%
    • Dedicated Compton polarimeters and Cherenkov detectors
    • Use upstream and downstream polarimeters
      • Machine feedback and access to luminosity-weighted polarization
    • Use also annihilation data: `average polarization’
      • Longterm absolute calibration scale, up to ΔP/P=0.1%

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

compton polarimetry at ilc
Compton polarimetry at ILC
  • Upstream polarimeter: use chicane system
    • Can measure individual e± bunches
    • Prototype Cherenkov detector tested at ELSA!
  • Downstream polarimeter: crossing angle required
    • Lumi-weighted polarization (via w/o collision)
    • Spin-tracking simulations required

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

expected depolarization effects
Expected depolarization effects
  • In general: two effects cause depolarization
    • Largest Effects during beam-beam interaction
    • Spin precession (T-BMT) and spin-flip (ST) effects
    • Have been compared for ILC and CLIC:
    • Theoretical updates due to strong field environment
    • See also talk by A. Hartin
  • Spin treatment in DR, spin rotators, BDS under work
    • See also talks by D. Barber

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

ew precision measurements@z factory
EW precision measurements@Z-factory
  • GigaZ option at the ILC:
    • high-lumi running on Z-pole/WW
    • 109 Z in 50-100 days of running
    • Needs machine changes (e.g. bypass in the current outline)
  • Dedicated Z-factory:
    • fraction of GigaZ
    • but strong physics case given already now!
  • Both facilities need polarized e- and e+ beams
    • Use of Blondel scheme required to get ΔP/P≤0.1%
  • Measurement of e.g. sin2θW with unprecedented precision achievable!

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

why electroweak precision data
Why electroweak precision data?

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

relevance of ew data today
Relevance of ew data today
  • Most sensitive observables: mW, sin2θeff,(g-2)μ,…
  • Large discrepancy between ALR(l) and AFB(b)
    • world average: sin2θeff=0.23153±0.00016

(central value, errors added in quadrature →brute force)

  • Impact of this measurement ?

←in b’s

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

measuring the ew mixing angle
Measuring the ew mixing angle
  • Measuring the AFB ,

ALR can be interpreted

as measuring sin2θW

  • LEP result:

sin2θW=0.23221±0.00029

  • SLC result:

sin2θW=0.23098±0.00026

    • Discrepancy between AFB and

ALR -> impact on Higgs tests !

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

m w vs central value sin 2 eff
mW vs. central value sin2θeff

→ Consistent with SM and SUSY

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

m w vs sld value sin 2 eff
mW vs. SLD-value sin2θeff

→ not consistent with the SM

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

m w vs lep value sin 2 eff
mW vs. LEP -value sin2θeff

→ not consistent with neither SM nor SUSY

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

what s the role of polarization
What’s the role of polarization?
  • Statistical uncertainty of ALR
    • If only polarized electrons:Δ ALR given by polarimeter uncertainty

→ depends on ΔσL, ΔσR, ΔP/P

→ main uncertainty at LC from ΔP/P~ 0.5 %→ 0. 25%...

    • If both beams are polarized: Blondel scheme

→uncertainty depends on ΔσLL, ΔσLR, ΔσRL, ΔσRR not on ΔP/P !

→Some running in LL and RR required, about 10-20% of the time

SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

blondel scheme for gigaz z factory
Blondel scheme for GigaZ / Z-factory

  • Measurement of sin2θ in e+e-→Z→f f :
  • With Blondel Scheme at ILC:
    • (80%,60%) : Δsin2θ= 1.3x10-5
    • but Δmtop= 0.1 GeV required!
  • With Blondel Scheme at a Z-factory:
    • and still Δmtop~1 GeV (i.e. before ILC run): Δsin2θ= 1x10-4 useful!
    • but polarized beams required, i.e. P(e+)≥ 20% !

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

summary
Summary
  • Polarized e- and e+ beams to optimize LC physics potential
    • Not only powerful for ‘chirality’ and couplings of new particles!
  • Physics potential of either GigaZ or Z-factory a.s.a.p.
    • Δsin2θ <1x10-4 seems reasonable now!
  • Special care of machine design needed to exploit polarization
    • High lumi source designs, spin rotators, precise spin tracking
    • Precise Compton polarimetry (up- and downstream)

…. But polarization is these efforts worth ! …

  • Further news on polarization at a LC
    • Webpages: www.ippp.dur.ac.uk/LCsources
    • Further spin effects under work, e.g. CP at LHC, LC, …..

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

relevance in worst case scenarios
Relevance in worst case scenarios
  • Hints for new physics in worst case scenarios:
    • Only Higgs @LHC
    • No hints for SUSY
  • Deviations at Zpole
    • Hints for SUSY
  • Discrepancy

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

slide40

mtop= 173.3 +- 1.1 GeV

  • Further important input quantities: mass of top
  • δsin2θ ~ 1 x 10-4 would be reasonable now (i.e. before ILC run) !

LHC

ILC

SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick