The LHCb Muon System and LAPE Participation Burkhard Schmidt CERN - EP/LHB Presented at the CNPq...

The LHCb Muon System

and LAPE Participation

Burkhard Schmidt

CERN - EP/LHB

Presented at the CNPq Workshop

Rio de Janeiro, 12 January 1999

12/1/1999 B. Schmidt / CERN

Outline

• IntroductionMuon identification in particle physics experiments

• The LHCb Muon System- Overview- Muon detector technologies and prototype studies- Frontend-electronics- Level 0 muon trigger

• Muon System Schedule

• LAPE Participation

• Conclusion


Introduction

Lepton identification:

• Many discoveries in particle physics are based on lepton (e, identification: J/Neutral Currents, W± and Z0, top etc.

• Lepton identification in LHCb is important for the Bd J/s and Bd J/(ee)s decay channels

• electrons and muons give complementary signatures due to huge differences in

radiative losses:

- electrons are identified by calorimetry and E/p matching- muons are identified by their penetration power

• The complementarity of e and signatures is a powerful tool inparticle physics

510322

.m

me


The LHCb Detector


Introduction

Hadron punch-through:

• The probability for a hadron to traverse material of thickness L and nuclear interaction length without interacting is e -L/ .

• Punch-through indicates the debris exiting an absorber and causeswrong identification of a hadron as a prompt muon.

• The length of a hadron absorber must be sufficient to reduce thepunch-through trigger rate well below the prompt rate.

• Minimum absorber length ~ 10

Total thickness of LHCb hadron absorber (muon shield) : ~ 23


Overview

Background sources in the LHC environment:

• primary background (correlated in time with the p-p interaction):- hadron punch-through including muons generated in the hadron shower

-K X decays, predominantly with PT< 10 GeV

• radiation background:neutron and photon “gas” (MeV energies from radiative n-capture) generated by hadrons interacting in the absorber. Its impact depends on the efficiency of the chamber material for photon conversions.

• machine background:energetic muons produced in beam-gas interactions and in machine elements upstream of the experimental areas.


Overview

Particle fluxes in the muon stations

• The highest rates are expected in M1(not protected by the shield)and in the inner part of Stations 2-5.

• In the outer part of station 2-5 a technology with moderate rate capability can be used.


LHCb Muon System

The Muon System must provide:

• Muon identification

• Reliable beam-crossing identification (good timing resolution)

• Reasonable momentum resolution for a robust PT-selective trigger(L0 muon trigger)

• Good performance for the duration of LHC in a high rate environment


Muon Detector Layout

Chamber pad structure:• Muon stations are devided in 4 regions with

different pad size• Pad dimension scales with station number

Projectivity to interaction point

• Required precision in the bending plane (x) leads to x/y aspect ratio of 1/2 in stations M1 and M2.

• “Physical” pads in outer region and in the various planes per station are grouped together to “logical” pads.

total number of physical pads: ~240 ktotal number of logical pads: ~45k


Muon System Technologies

Cathode Pad Chambers (CPC) :• Wire Chamber operated in proportional mode with cathode pads (strips)

providing the spatial resolution.

wire-spacing s determinestime resolutionat present: s = 2mm

• Characterized by very high rate capability and moderate time resolution• 30% CO2, 60% Ar and 10% CF4 is prefered gas mixture • CPC have good aging properties:

4C/cm equiv. to 50kHz/cm2/s for 10years



Status of CPC R&D:• A first prototype with pads of different sizes has been constructed

together with its frontend-electronics at PNPI and tested using theCERN-PS beam.

• good signal/noise separations have been obtained • time resolutions are better then expected



Resistive Plate chambers (RPC) :• Type of parallel plate chamber (therefore simple construction)

with plates of a bulk resistivity of ~ 1011cm

• Gas mixture normally used: C2F4H2 + few % isobutane + 1% SF6

• RPCs provide excellent time resolution and a moderate rate capability.


Muon System TechnologiesMultigap RPCs (MRPC) :• Improve timing properties of RPC further and reduce streamer formation



MRPC R&D:• Participants: CERN and UFRJ-Rio

• Objectives: - Studies of resistive plates (materials)

- Development of construction techniques

- Performance studies in testbeam

• Status: - First (small) prototype has been tested last year- prototype of 130cm x 230cm is under construction and will be studied this year using testbeams.


Muon Frontend Electronics


L0 Muon TriggerAlgorithm (I) :

• start with pad hit in M3 (seed)• extrapolate to M4 and M5 and look for hits within field of interest (FOI)• search for hits in M2 and M1 and take hits closest to centre of search window• calculate x- and y-slopes and find y-intercept at z=0


L0 Muon TriggerMuon Momentum Measurement:• Muon momenta are measured by means of the magnet spectrometer.• In the bending plane the deflection angle is given by:

• The transverse momentum PT is given by: PT = P tan2 dim. tan )

The momentum resolution is limited by: • multiple scattering (material between IP andM2)• the granularity of the muon chamber pads• magnetic field map and alignment


L0 Muon TriggerDistributions of P and PT for muons:

Title:ptt_rio_nor.epsCreator:HIGZ Version 1.23/09Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.


L0 Muon Trigger

• Algorithm (II):

• calculate muon PT

(PT -resolution is ~25%)

• apply cut on PT:

1GeV< PT<2GeVB X efficiency of 8% -14% MB-retention of 1% - 3%

(region of LHCb operation)


Muon System Schedule

• Optimization of the muon detector

• Study of MRPC and CPC (WPC) prototypes in testbeam

• Design and and develop FE-electronics • Accommodate L0 muon trigger to detector layout

• Choice of technologies for detector and electronics

• Finalize detecotor design

• Construction and test of full scale prototypes

• Technical Design Report (TDR)

• Construction and test of muon chambers

• Installation and commissioning of the muon system

1998

1998 + 1999

1998 + 1999

1998 + 1999

January 2000

July 2000

2000

January 2001

2001 - 2003

2004


LAPE Participation in the Muon Group

Present situation:Physicists from UFRJ Rio de Janeiro are involved in various aspectsof the muon system, in particular :

- the research and development of MRPC,- the development of the related frontend-electronics,- the implementation of the L0 muon trigger.

Future Possibilities:• UFRJ can be a major production-center of the muon chambers and the

frontend electronics.

• This will open a door to brazilian industry and result in an important

technology transfer.


Conclusion

Physicists form UFRJ Rio de Janeiro are making a major contribution to the muon

project of the LHCb experiment.

The contribution of LAPE to LHCb is important for the experiment and has

certainly a positive impact for science and industry in Brazil.

The LHCb Muon System and LAPE Participation Burkhard Schmidt CERN - EP/LHB Presented at the CNPq...

Documents

Transcript of The LHCb Muon System and LAPE Participation Burkhard Schmidt CERN - EP/LHB Presented at the CNPq...