High Energy Experiment

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HEP Journal Club
High Energy Experiment Detector (2)
2009. 2. 19 Kihyeon Cho
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Experiments related to CKM parameters
ee- B Factories
Major experiments ongoing, some ended
Talk by Elisabetta Barberio
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Super Belle (2012)
http//www.kek.jp
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Heavier B gt Full Service of B factory
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???-??? ?? ??? ?? (Large Hadron Collider)
CERN
LHCb
ATLAS
CMS
ALICE
LHC at CERN
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High Energy Experiments Detector

• Multipurpose detector
• A variety of detectors
• 4 pi hermetic detectors
• Large cost and long time development and
  construction
• High end technology involved -gt applied to
  industry (so many examples)

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HEP detector
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High Energy Experiments Detector

• Particles are detected via their interaction with
  matter
• Different physical processes
• For charged particles predominantly excitation
  and ionization
• The common methods for particle identification
  are
• Vertexing and Tracking particles through a
  magnetic field.
• Thin (low Z) material
• Gas, liquid, solid
• Energy loss measurement
• Calorimeter
• High-Z material (absorber)
• ID of particles like Cerenkov
• Others like Time of flight

See http//public.web.cern.ch/public/
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Tracking Particle through a Magnetic Field

• Gas detectors MWPC, TPC, Drift Chamber, GEM,
• Solid State (Silicon) detectors PIN diode, CMOS,
  CCD, (Pixel, Strip, ..)

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• Momenta of charged particles can be measured in a
  relatively straightforward fashion using magnetic
  spectrometer.
• In certain situations, however, magnetic
  measurement may not be viable. For example,
  precise magnetic measurements becomes difficult
  and expensive at very high energies because they
  require either large magnetic fields in extended
  regions of space, or very long lever arms for
  measuring small changes in the angular
  trajectories of particles passing through
  magnets, or both.
• In addition, magnets can not be used for
  measuring energies of neutral particles.
• Calorimeters are then used to measure the total
  energy deposition in a medium.

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Calorimeters
A calorimeter is a device that absorbs the full
kinetic energy of a particle, and provides a
signal that is proportional to that deposited
energy.
EM particles (EM Cal.) Hadrons (Hadron Cal.)

• Gas detectors MWPC, GEM,
• Solid State (Silicon) detectors PIN diode, CMOS,
  CCD, (Pixel, Strip, ..)
• Scintillation detectors Crystal, Plastic,

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Energy Loss

• dE/dX Counter
• A counter telescope consists of two or more
  detectors through which a charged particle passes
  in sequence, usually stopping in the last one.
  The fraction of energy dE it loses in the passing
  detectors is a measure of the stopping power. The
  stopping power (given by Bethe-Bloch formula to
  be discussed in a few weeks) varies approximately
  as z2/v2 or mz2/E, where v is the speed of the
  particle of mass m and charge ze. The energy E is
  obtained by summing the signals from all the
  detectors, and the product E x dE is roughly
  proportional to mz2. A graph of DE versus E gives
  a family of hyperbolae, each corresponding to a
  different values of mz2. For light ions with
  sufficient energy, this often is enough to
  identify the ion uniquely. However, this method
  is limited by the finite energy resolution of the
  passing detector.

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Global 5-parameter fit for phmp_nml vs

• binning with nearly the same statisticsat each
  point to reduce the error
• Using garbage events in order to fastly calibrate
  this curve for BESIII in future
• A uniform formula to avoid discrete expression
  for density effect
• The curve fit the BESII data OK

Beam-gas proton
Radiative bb
Cosmic rays
BESII data
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Time of Flight

• Time of flight (TOF) measurements have important
  applications in providing discrimination between
  particles of similar momentum but different mass
  that may be produced from a reaction.

For two particles of mass m1 and m2, the time
difference will be given as
For p1 p2 p,
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Introduction Gas Cherenkov Detectors

• Detection of Cherenkov light
• v gt c/n in medium (refraction index n)
• ß c/v
• cosf1/nß

Reference http//encyclopedia.thefreedictionary.c
om/Cherenkov20effect
HBD ? Violet Ultraviolet (VUV) light
detection
Georgia Karagiorgi, FAS 2005
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Cherenkov Detector

• When a charged particle moves with uniform
  velocity in vacuum, it does not emit radiation.
  However, if it travels in a dielectric medium of
  index of refraction ngt1, and with a speed greater
  than the speed of light in that medium (I.e. v gt
  c/n), then it emits what is known as Cherenkov
  radiation (after Pavel Cherenkov, who first
  observed the effect in 1934). The direction of
  the emitted light can be calculated classically
  using Huygens wave construction, and can be
  attributed to the emission of coherent radiation
  from the excitation of atoms and molecules in the
  path of the charged particle. The effect is
  completely analogous to the shock front
  produced by a supersonic aircraft.
• The emitted light has a spectrum of frequencies,
  with the most interesting component being in the
  blue and ultraviolet band of wavelengths. The
  blue light can be detected with relatively
  standard photomultiplier tubes, while the
  ultraviolet light can be converted to electrons
  using photosensitive molecules that are mixed in
  with the operating gas in some ionization
  chamber. The angle of emission for Cherenkov
  light is given by

Registration by Cherenkov detector
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• The intensity of the produced radiation per unit
  length of radiator is
• proportional to sin2qc. Consequently, if bngt1,
  light will be emitted, and if bnlt1, no light can
  be observed.
• Cherenkov Detector Types
• Threshold Cherenkov counter Based on the choice
  of the index of refraction of a given radiator
• Differential Cherenkov couter Based on the light
  cone angles for different particles for the same
  n

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Neutron Detector

• A neutron detector does not record the presence
  of a neutron directly but responds to secondary
  radiation (generally fast charged particles)
  which is emitted when the neutron undergoes a
  nuclear reaction in the detector medium.
• For slow and thermal neutrons, the (n,p),
  (n,alpha) or (n, fission) reactions on light
  nuclei are among those most commonly used in
  detectors. Many of these reactions exhibit a 1/v
  dependence at low energy, giving high cross
  sections for thermal neutrons.
• For fast neutrons of several MeV, scattering off
  a light target can give enough energy to a
  recoiling nucleus for detection.

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References

• Prof. Il Heung Park, Summer School (2006.06.17)

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Recommended to Students

• Recommended Books
• K. Kleinknecht - Detectors for Particle
  Radiation, C.U.P.  1990
• R.K. Bock A. Vasilescu - The Particle Detector
  BriefBook, Springer 1998  (see below)Alternatives
  R. Fernow - Introduction to Experimental Particle
  Physics, C.U.P. 1986
• W.R. Leo - Techniques for Nuclear and Particle
  Physics Experiments, Springer-Verlag  1987
• G.F. Knoll - Radiation Detection and Measurement,
  Wiley  1989 
• Other resources
• Web version of The Particle Detector BriefBook 
  http//www.cern.ch/Physics/ParticleDetector/BriefB
  ook/
• CERN notes Fabjan Fischer - Particle Detectors
  CERN-EP 80-27, Rep. Prog. Phys. 43 (1980) 1003.
• Sauli - Principles of Operation of Multiwire
  Proportional and Drift Chambers  CERN 77-09