Resolutions in the central tracker without the Mvd system GSI, 10 June 2014 Resolutions in the central tracker without the Mvd system Gianluigi Boca

the base macros I used to make the analysis ! Nowadays we are talking about resizing the PANDA experiment for budgetary reasons; This is a study with a single track and no pileup (so already an idealized situation) on how bad the momentum and angular resolutions become when no Mvd hits are used (but the material is still there). Many thanks to SUSANNA for providing me the base macros I used to make the analysis !

Muons are generated at 3 momenta : 1, 2 and 3 Muons are generated at 3 momenta : 1, 2 and 3.5 GeV/c in  bins covering the angles from 20 up to 140 degrees; each bin is 2 degrees wide The Kalman filter is run with 1 iteration (1 come and go) or with 3 iterations. Different results are obtained in the two cases.

Momentum resolution at origin (without Mvd hits)

1 Kalman iteration

(p)/p (in %) at point to closest approach to origin muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

Results don’t change much 3 Kalman iterations Results don’t change much

(p)/p (in %) at point to closest approach to origin muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

 angular resolution at origin (without Mvd)

1 Kalman iteration In the absence of the Mvd hits, the angle  is determined by the skew straws; consequently you will see that the resolution worsens considerably with respect to the usual 1-2 mrad.

() (in mrad) at point to closest approach to origin muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

Resolution becames  20 % worse and shape changes drastically 3 Kalman iterations Resolution becames  20 % worse and shape changes drastically

() (in mrad) at point to closest approach to origin muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

 angular resolution at origin (without Mvd)

1 Kalman iteration In the absence of the Mvd hits the  angle is determined by the axial straws, therefore the resolution gets worse the the usual couple of mrad but less than the  resolution.

() (in mrad) at point to closest approach to origin muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

Resolutions are a couple of percent better.. 3 Kalman iterations Resolutions are a couple of percent better..

() (in mrad) at point to closest approach to origin muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

I did the same exercise to see how the Dirc would be affected In the following you can see the  and  resolution at the Dirc entrance point, when using 1 or 3 Kalman iterations.

 angular resolution at the Dirc (without Mvd)

1 Kalman iteration

() (in mrad) at entrance point to Dirc muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

… for comparison, the same distributions but with the Mvd hits used 2 GeV/c 1 GeV/c 3.5 GeV/c

You see that resolutions get worse and shape changes dramatically 3 Kalman iterations You see that resolutions get worse and shape changes dramatically

() (in mrad) at entrance point to Dirc muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

… for comparison, the same distributions but with the Mvd hits used 2 GeV/c 1 GeV/c 3.5 GeV/c

 angular resolution at the Dirc (without Mvd)

1 Kalman iteration

() (in mrad) at entrance point to Dirc muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

… for comparison, the same distributions but with the Mvd hits used 2 GeV/c 1 GeV/c 3.5 GeV/c

3 Kalman iterations In this case the resolutions get better….

() (in mrad) at entrance point to Dirc muons, single track, generated in bins of 2 degrees in  no Mvd hits are used 1 GeV/c 2 GeV/c 3.5 GeV/c

… for comparison, the same distributions but with the Mvd hits used 2 GeV/c 1 GeV/c 3.5 GeV/c

The bloody CONCLUSIONS 1) The momenmum resolutions become  1.5 worse, could we live with that ? 2) The  resolutions become terrible both at the origin and at the Dirc and also the  resolution gets 2 or 3 Times worse → the Dirc could not work and the secondary vertex finder neither.