The focusing mirror systemThe focusing mirror system

Preliminary studies with mirrors (to reduce instrumented area): - focalization capabilities shown - ring patterns for positive and negative mesons at different angles and momenta reconstructed

• spherical (elliptical) mirror within gap volume for backward refl. • plane mirror just beyond radiator for forward reflections

Different scenarios (refractive index, radiator thickness, mirror geometry) are being explored

TOF

Reflectinginside

direct &reflected

Low materialbudget

Minimize detector area (~1 m2/sector) interference with FTOF

Hit prob

Hit prob > 3 10-4

Hit prob

Hit prob > 3 10-3 200 trials per pointAerogel: - n=1.06 - thick. increasing with radius: 2-4-6-8-10 cm

Mirror: 14-25o

PMTs: UBA

Hybrid ring example:

200 trials per point

Aerogel: - n=1.06

- thick. increasing with radius: 2-4-6-8-10 cm

Low angles more challengingThe same with increased number of trials

LH-LHk,p : Mirror 14-25o PMTs: UBA

Protons benefit the smallnumber of unfired PMTs whit expected signal(P is small when C=0)-

200 trials per point

Aerogel: - n=1.06

- thick. increasing with radius: 2-4-6-8-10 cm

N p.e. > 5 for reflected ringsN p.e. > 12 for direct rings

Average N p.e. : Mirror 14-25o PMTs: UBA

200 trials per point

Aerogel: - n=1.06

- thick. increasing with radius: 2-4-6-8-10 cm

Average N p.e. : Mirror 14-25o PMTs: UBA

Mirror is mandatory for positive hadrons and gives benefit for negative hadrons at large angles and small energy

Big dot = studies show in the previous slide

200 trials per point

Aerogel: - n=1.06

- thick. increasing with radius: 2-4-6-8-10 cm

Average N p.e. : PMTs: UBA

Mirror up to 35o:Worse for positive hadronsBetter for negative hadrons

200 trials per point

Aerogel: - n=1.06

- thick. increasing with radius: 2-4-6-8-10 cm

Average N p.e. : PMTs: UBA

Mirror up to 35o:Worse for positive hadronsBetter for negative hadrons

Average N p.e. : PMTs: UBA

Mirror 14-25o Mirror 14-35o

Worse for positive hadronsBetter for negative hadrons

LH-LHk,p : PMTs: UBA

Mirror 14-25o Mirror 14-35o

Worse for positive hadronsBetter for negative hadrons

100 trials per point

Aerogel: - n=1.06

- thick. increasing with radius: 2-4-6-8-10 cm

M35 is acceptanble but slightlyworse for positive and does not improve at large angles ?!

Average N p.e. : Mirror Angle Coverage (UBA)

100 trials per point

Aerogel: - n=1.06

- thick. increasing with radius: 2-4-6-8-10 cm 2-2-10-10-10 cm 3-5-5-10-10 cm

With 2-10 middle-angles improveWith 3-10 only small angles improve

Average N p.e. : Aerogel thickness (UBA)

100 trials per point

Aerogel: - n=1.06

- thick. increasing with radius: 2-4-6-8-10 cm

Symmetric EllipsoideSemi-Axes focalizing onto the photon detector best in Npe

Average N p.e. : Mirror Semi-axes (UBA)

Semi-reflective Mirror

Different dielectric or thin metalized film toincrease the rflection coefficient at 0o (normal)

Angle dependence stays with similar Brewster angle Here =atan(n2/n1) ~ 64o

Semi-reflective Mirror in Geant 4

R and T defined by n1,n2

Only way so far: fake dielectric materialwith refraction index ~ 5 to modify R/T ratio to fifty-fifty.

Brewster angle ~ 79o

Put at zero Lobe and Back reflection Diffusion

Next: Take lobe and remove spike to play with surface roughness

100 trials per point

Aerogel: - n=1.06

- thick. increasing with radius: 6-6-6-10-10 cm

Same performance withIncreased aerogel thickness

Can improve high angles only

Average N p.e. : Semi-reflective Mirror (UBA)