A light Higgs boson mh200 GeV - PowerPoint PPT Presentation

Title: A light Higgs boson mh200 GeV


1
A light Higgs boson (mhlt200 GeV) might mean
Supersymmetry (SUSY)

• pro SUSY
• solves theoretical problems of scalar Higgs
  field
• may allow gravity to be unified with the other 3
  forces
• one version predicts the size of ElectroWeak ?Z
  mixing
• lots of new particles to look for Higgses and
  superpartners
• - at least two extra neutral Higgses (h0, H0
  and A0) and H, H-
• - spin 1/2 leptons and quarks have scalar
  slepton and squark partners
• - integer spin ?, W, Z, Higgses have spin 1/2
  gaugino partners
• provides candidate for astrophysical dark
  matter
• Minimal Supersymmetric Standard Model (MSSM)
  wants
• mh present best-fit value.
• against SUSY
• no direct evidence so far
• adds at least as many parameters as it explains,
  e.g. tan?, mA
• an infinite set of possible SUSY breaking schemes

2
Is it a SUSY Higgs?
TESLAs precision values for the ratios of
couplings can differentiate between SM and SUSY.
Note mAlt500 GeV is incompatible with SM ratios.
3
Covering the Wedge
Plot shows how many of the MSSM Higgses LHC will
see at each value of tan? and mA
LHC cannot tell SM fromMSSM Higgs in the wedge
at medium tan?
But previous slide shows precision Higgs
couplings with SM values would disprove MSSM
with mAlt500, even if only h0 seen. Alternatively,
the precision couplings could lie on the MSSM
trajectories. Would be powerful evidence for
it (or something like it).
4
SUSY Partners at TESLA
Many possible schemes, for example
Spartner pair- production limit at 800GeV TESLA
Spartners light enough to be produced at TESLA or
LHC will be copious TESLA can sort out more
precisely.
5
The EWSB Labyrinth what TESLA is required to do
(After Francois Richard)
Y
SUSY?
Explore
SSB mechanism
N
N
SM?
Higgs properties
Y
New Signals?
Explore
Y
Y

N
Quantum Level including GigaZ mt,
Mh, sin2?W, ???
Higgs at LHC or TeV?
N

N
NO Higgs! Confirmed at Linear Coll.?
NDgt4?
Y
Instead of SUSY WHAT?
Explore
TC?
No new physics (yet)
no exit without a Linear Collider
6
TESLA needs 104 times SLCs Luminosity,
103 times LEPs
frep bunches/second Ne electrons/bunch
?x rms bunch width ?y rms bunch height

Luminosity formula (simplified)

• A decade of RD, at SLAC, DESY,
• KEK etc. has given
• ?100 improvement on the top line
• more bunches with more charge.
• 1/100 reduction in ?y to 5 nm,
• lower emittance (brighter beam) ,
• more demagnification.

7
Building blocks for a linear collider FEL (all
have worked in prototype NLC/JLC similar.) TESLA
Test Facility already at design gradient
Free Electron X-ray Laser
30 GeV e- undulators 200 GeV e-
Reduces phase-space - transverse ? emittance, -
longitudinal ?p/p, by Syncrotron Radiation.
e cooling rings
e source
?-rays
e- linear accelerator
e- cooling ring
e- source
e linear accelerator
E
e- bunch
Niobium cavities. E field reverses once per
cycle, accelerating in-phase particles
8
Where the bits are in TESLA
9
The Free Electron Laser for condensed matter
studies of all kinds
So TESLA gets SASE. Undulator has
periodic magnetic field ?undcm. Electrons lag by
1 X-ray wavelength per undulator period, so
Synchrotron Radiation photons are coherent. Worke
d for U.V. in 2000 at TESLA Test
Facility. Intensity goes like Ne2 (TESLA better
than NLC) and beam must be very parallel low
emittance.
10
Beam parameters from a typical TESLA
FEL undulator
?X-ray ?und(1K2)/2?2
a few cm
undulator parameter
(Ee/me)2
For a given undulator, increase Ee to get
shorter ?X-ray. Need 10s of GeV for ?X-ray
1A
11
Space and time structure of the FEL X-rays
With spot size100?m, divergence 0.8?rad, could
use ultra- grazing incidence mirrors (or low-Z
diffraction) to make 50 nm focal spot, if needed.
SASE sharpens X-ray bunch length (red
100fs) from electron bunch length (dotted, 200
fs). Individual peaks coherent longitudinally
within 0.3fs.
12
Comparison of TESLA and LCLS (Stanford) peak
brilliance with exisiting 3rd gen. Undulator
sources. SASE makes a big difference.
13
Applications discussed in TESLA TDR
Ill try and explain two of the examples...
14
e.g. 1. Trans-cis isomersation of stilbene (one
of many pump-probe applications using the
time resolution of the FEL linked with an optical
laser)
The optical laser pump starts the two phenyl
moieties swinging, then the X-ray probe pulse
shows how far they have swung. Relaxation time
4 ps.
(scaled scattering angle)
15
e.g. 2. Snapshots of single macromolecules
It takes a finite time for the atoms to move,
even if X-ray intensity is enough to
destroy binding. At predicted FEL intensity
there will be a coherent diffraction
pattern containing full information about the
initial atomic configuration.
Many important molecules cannot be crystalised,
or loose properties if they are.
Simulation of Coulomb explosion of T4 lysosome
molecule (H white, C grey, N blue, Ored, S
yellow) at three stages during 3x1012 /(0.1?m)2
pulse of 12.4 keV X-rays. Distortion much
smaller at lower intensity.
16
e.g. 2 continued. Combine successive diffraction
patterns to build up detailed distribution
Example of Bluetongue virus (BTV) capsid. LHS -
diffracted intensity from 3x1010/(0.1?m)2 photon
s. Only low resolution information, but enough
to align pattern
RHS - Plane section of molecular transform of BTV
capsid. Multiple oversampled single molecule
transforms can be aligned and added to build this
up in reciprocal space, allowing real-space
electron distribution to be computed.
17
e.g. 2 continued.
The single molecule FT contains more information
than a crystal FT. IF the diffraction images
can be aligned then full structure is there.
Single molecules may be contained in microspay
drops or attached to known structure - e.g.
virus capsid.
18
Conclusions
1. Particle physicists must get their act
together internationally (good progress with
ECFA in Europe, HEPAP in USA). OECD panel will
report next year. TESLA in Chicago a possibility,
if US comes up with more money than Germany. 2.
X-FEL users,of all kinds, are encouraged to
explore the potential. 3. Accelerator designers
need more support for fundamental developments.
PPARC trying to make common cause with MRC,
EPSRC, CLRC etc. to revive accelerator and FEL
physics in UK. Daresbury is thinking of its own
hard-U-V FEL. 4. Fantastic detectors will be
needed for X-FEL experiments - space and time
resolution far beyond present performance. 5.
Programme will absorb (in both senses) a lot of
good physics graduates and Ph.Ds.