The Tesla muon detector an update Marcello Piccolo St. Malo April 2002

Marcello Piccolo2 Agenda b A reminder of the TDR b Performances with single muons b Pions rejection ( single particles ) b Punch through and decays b Multijet environment b Some R&D results b Conclusions

Marcello Piccolo3 TDR reminder b The design is based on a long octagonal barrel. b The end caps are completely encompassed by the barrel octagon. b The barrel itself is longitudinally segmented in three pieces b Transverse segmentation is 10 cm in the first 100 cm of Fe absorber. b In order to minimize the total detector area the last 30% of the absorber does not house any active detector: one last plane is foreseen after the absorber itself.

Marcello Piccolo4 TDR reminder b Total Fe thickness 150 cm. b (Some) Calorimetry capability built in. b Just a muon tagger... Limited momentum measurements capabilities. b Threshold momentum around 5 GeV/c with 4 Tesla B field. b Full efficiency ( > 95% ) above 8 GeV/c  Angular coverage complete  min ~ 100 mr.

Marcello Piccolo5 TDR reminder 8/11 planes  planes

Marcello Piccolo6 Single particle performances b Here is the response to muon (full) and pions (dashed) b The overall normalization for the input spectra differs by a factor of 5. 5 times more pions than muons.5 times more pions than muons. b The vertical axis is logaritmic. b The overal rejection is better than 0.3%.

Marcello Piccolo7 Single particle performances (cont.) b In order to asses the overall goodness of the design, one should see if the misidentified pions come from punch through or from decay, b The optimized confguration obviously calls for a mix of the two components. b Here is the truth table for misidenfied pions propagating in the calorimetric part of the Tesla detector b These results come from a particles generated with a flat momentum and angle spectra.

Marcello Piccolo8 Moving to a jetty environment A first analysis has been performed on bb events in the barrel region. Here is the momentum spectrum for particles ending up in an angular region between 0.81 and 2.35 rad. (polar angle).

Marcello Piccolo9 And comparing to muons  

Marcello Piccolo10 Applying a naïve  identification algorithm  Require a  -stub crossing at least 8 planes out of 11. b The stub is defined by angular consistency of the hits. b Matching a charged track in angle to the first hit of the stub results in the operational muon definition.

Marcello Piccolo11 Here are the overall results The four spectra refer to: RED : generated primary particles particles GREEN: generated  BLUE : identified  YELL : misidentified 

Marcello Piccolo12 Performances…good enough? b Identification efficiencies seem O.K. b Pion rejection is 100 to 1. b If anything, one would ask a better pion rejection: an identified muon, in this class of events, has a 30% chance of being a misidentified pion. b Why this deterioration with respect to the single particle figure ? b Fake associations are the first bet.

Marcello Piccolo13 Performances in bb jets b Let’s go to the truth table again, and check the relation between the hits in the first layer and the associated track (for misidentified hadrons).

Marcello Piccolo14 More in detail..

Marcello Piccolo15 So, performances could be improved b Fake association do account for a sizeable part of fake muons…. Better software might get rid of a good part of them.Better software might get rid of a good part of them. b Better extrapolation of charged tracks should be used : a first step can be the GEANE package. b As of now the matching is pretty crude: an angle cut both in polar and azimuthal view.

Marcello Piccolo16 Looking at figures… b Assuming to be able to get rid of all the fake associations one would end up with the following background counts:       b Comfortably close to the single particle numbers

Marcello Piccolo17 Can the limiting rejection be reached ? b This is a detailed question that can be answered only with a complete simulation. b I believe that some optimism is warranted: the achievable spatial resolution of RPC’ has not been used in the preliminary analysis shown before. b Proposed devices would allow spatial resolutions close to 0.5 cm. ( close to 1 mrad. at the radius of the first layer): the matching I used in what has been reported was based on a 40 mrad. cut.

Marcello Piccolo18 Last simulation topic: how about a muon trigger ? b Using a hit-stub to define a muon trigger one can evaluate which kind of rate and purity can be achieved. b Here is a plot of the particle content of a 8 planes stub in bb events.

Marcello Piccolo19 Detector R&D b Now let’s switch gear and move to a different topic…. b Up to now, in the simulation, detectors were a porridge of materials linked to a given spatial and/or energy resolution. b We would like now to prove that the figures we used are indeed achievable in a sort of routine way, as the overall number of detectors calls for a mass production.

Marcello Piccolo20 Parameters to be shown  The design of the  detector calls for efficient devices capable to yield space resolution of cm. b I will then show typical efficiency maps for a single gap RPC. b Spatial resolution achievable on large detectors (2 m 2 ) will also be shown.

Marcello Piccolo21 Test set-up b A cosmic test facility is operational in Frascati: it consists of 10 shelves to house RPC’ s up to 3x1 m 2. b Two more RPC on top and bottom provide trigger and tracking. b Electronics to read out the struck strips is the standard BaBar electronics. b Typical trigger rate is about 40 Hz; data are read into a DAQ pc essentially at the same rate. b A slow monitoring stream to check currents and temperatures has been implemented too. b Most of the work on this setup has to do with BaBar, it is, however easy to plan measurements relevant to the muon detector for a linear collider apparatus

Marcello Piccolo22 A typical efficiency map

Marcello Piccolo23 Spatial resolution b Typical resolution plot. b The spike is well represented by a single gaussian. b Ratio between areas of the two gaussians used in the fit is roughly 10:1. b Overall resolution is b 0.66 cm

Marcello Piccolo24 R&D to do list b Local rate capability measurement Assumed 10 hits/cm 2 in streamer mode.Assumed 10 hits/cm 2 in streamer mode. b Test performances with and without linseed oil. b Test different mixtures to minimize sensitivity to slow neutrons. Minimize Hydrogen content of gas mix.Minimize Hydrogen content of gas mix. b Test different working regimes Avalanche could allow an extra factor of 10 in local rateAvalanche could allow an extra factor of 10 in local rate A possible alternative as had-cal active device.A possible alternative as had-cal active device.

Marcello Piccolo25 Outlook and Conclusions b The design philosophy for the muon detector doesn’t seem to show major flows.  More detailed simulation needed to evaluate  rejection rate in jetty events. b R&D studies started Basic requirements for the proposed detectors on hand.Basic requirements for the proposed detectors on hand. More features of the proposed detectors to be investigated …might even be used in the had-cal.More features of the proposed detectors to be investigated …might even be used in the had-cal.