LHC

The Large Hadron Collider (LHC) is an accelerator with 27 km circumference.

Being built on the France-Switzerland border west of Geneva.

It will start to run at 2007.

High luminosity: 1034 cm-2s-1 High center of mass energy: 14 TeV

p – p collisions every 25 ns

CMS EXPERIMENT

• Compact Muon Solenoid (CMS) detector has been designed to cleanly detect the diverse signatures from new physics by identifying and precisely measuring muons, electrons and photons over a large energy range and at high luminosity.

• The main physics interests:

– Standard Model (SM) Higgs boson

– Minimum Supersymmetric Standard Model(MSSM)Higgs bosons

– Gluino, squark searches

The Calorimetry The Electromagnetic

Calorimeter (ECAL) is designed to measure the energies of the electrons and the photons with high precision.

Hadron calorimeter (HCAL) surrounds the ECAL to measure the energies and the directions of particle jets, and to provide hermetic coverage for measuring missing PT.

HCAL composed of three parts: HB , HE and HF .

HE & HB (Sampling calorimeters)HF– Two located at each end – Complete the HCAL coverage to |η|

=5– Steel absorber plates with quartz

fibers inserted into them, radiation hard

Super LHC

• The nominal LHC performance resulting in a luminosity of L ≈ 1034 cm-2s-1 in CMS

• The luminosity will be upgraded (2010) to L ≈ 1035 cm-2s-1

• The physics potential of SLHC

– accuracy in determination of SM (Standard Model) parameters

– accuracy in determination of New Physics parameters

– extension of discovery in high mass region

– extension of accuracy of rare physics

R&D STUDIES FOR SUPER-LHC CONDITIONS

• Scintillators are used in hadronic calorimeter up

to |η| < 3. • They loose half of their light output after a dose

of about 50 kGy. • CMS hadron calorimeters in the barrel region (|η|

< 1.5) will not experience radiation problems.• Scintillators in HE calorimeter will loose their

efficiency due to high radiation.

Scintillator sheets along with waveshifting fibers.

As a solution to the radiation damage problem in SuperLHC conditions, quartz plates are proposed as a substitute for the scintillators at the Hadronic Endcap (HE) calorimeter.

We are performing R&D studies on the quartz plates to find the most efficient way to get light out of them.

Quartz Plates as Radiation-Hard Detectors

• Quartz plates will not be affected by high radiation, but with quartz the light is from Cerenkov radiation.

• The Challenge: To develop a highly efficient method for collecting Cerenkov light in quartz.

• With the quartz plates, we propose to collect photons in the range from 400 to 200 nm and re-radiate them as blue at ~420 nm.

Cerenkov radiation vs Scintillation photons

• The Cerenkov detectors can be very fast.

• Low level of light is produced: about 100 times smaller than scintillator.

• Unlike scintillation light, Cerenkov photons are emitted along the direction of the particles velocity.

• Number of photons produced per unit length per unit wavelenght is proportional to 1/λ2 concentrated in short-wavelength region.

Fiber Geometries on Plates

HE GEOMETRY Y SHAPE S SHAPE

S&O SHAPE PEACE SHAPE NEW SHAPE

Tests Performed

• Light Collection Tests– We tested HE Scintillator, UVT Plates (3mm and 6mm thicknesses with 4

different geometries) and GE-Quartz plate in M-Test area at FNAL, with 120 GeV Proton beam.

• Surface Uniformity Tests– We tested all quartz fiber geometries for surface light collection non-

uniformities with UV-LED (380nm), Nitrogen Laser(337nm), and Mercury lamp.

• Radiation Damage Studies– Seven sets of quartz in the form of fiber are irradiated in Argonne IPNS for 313

hours.

Light Collection: Non-Uniformity

Assume the center of the plates has 100% efficiency

Y-Shape: Min = 48% Max = 253% Ave = 80%

O-Shape: Min = 14% Max = 614% Ave = 127%

S-Shape: Min = 48% Max = 253% Ave = 80%

Light Collection Efficiencies

Light collection efficiency ratios calculated as the ratio of total number detected photons by PMT during surface scans for each fiber geometry:

O : S : Y = 1 : 9.9 : 11.4

Both Y- and S- have better light collection efficiencies than O-shape.

Surface Uniformity Tests

Surface NonUniformity

0

20

40

60

80

100

120

S-Shape Y_Shape HE Shape PEACE

No

nU

nif

orm

ity(

%)

BLUE_LED

UV_LED

MERCURY

S-Shape gives more uniform signal.

All the others have a surface non-uniformity around 60%.

Radiation Damage Studies

• Low OH solarization quartz is a better UV transmitter than High-OH quartz.

• Polymicro manufactured a special radiation hard solarization quartz plate.

Conclusions

With final quartz plate design %90 light collection of scintillators

solution to the radiation damage problem

Future Plans

• We will continue with the tests/simulations and with testing possible improvements to attempt to obtain as much light as possible from the plates.

• We are ready for the next step : “Quartz Plate Calorimeter Prototype”