Report on PISA progress ~Small Addendum~ Takao Sakaguchi

Recall the Geometry nesting Maxim is aware of a problem –Amount of photon conversion did not change at all when Maxim added FEM to HBD –Sound somewhat bigger problem Geometry nest in HBD: –HALL (PHENIX)  HBDG (Gas Volume)  TISO (HBD Mother frame) –Most of HBD components (HV panel, GEM, etc.) attribute under “TISO” –I added shade under “TISO”, but no particle including photon interact with the shade A solution found by Maxim was to expand “GSM”(Gas volume include CsI of Top GEM and Mesh) that were already defined, and assign shade under GSM. –Maxim confirmed that the shade absorbs cherenkov photons

Electrons to PISA Threw pT=2GeV/c electrons into –|y|<0.5, and |  |<0.075 , Covers W4. –Histograms number of p.e. as a function of electron hit positions Counted cherenkov photons as a function of hit position of electrons. Z bin: 3cm from -30 to 30cm, Phi bin: ~ 4 deg. In the following slides, I show four (+one) cases –1, No Shade. PISA as is in PHENIX official library –2, In case of expanding “GSM” region (so to include shade in it), but no shade yet (slashed this time) –3, Mylar shade in PISA (in GSM) (2.5cm*2.5cm*2.5cm) –4, “Gas” shade in PISA (in GSM) (slashed this time) Suggested by Sasha a week ago. –5, Mylar shade in PISA (in GSM) (1cm*1cm*1cm) (added this time) Sorry, statistics is half of other cases..

Case 1: No Shade (Integrated) Integrated over all the events –Reasonable numbers –Tail may come from electrons hit in edge

Case 1: No Shade (phi-slicing) 4deg. Phi slicing (from -6 to 34 deg.) –Detector sits between 0 to 27 deg.. –Z: cm. 0 means middle of the detector –Y-axis: Number of photons per events

Case 1: No Shade (z-slicing) 3cm z slicing (from -30 to 30 deg.) –phi: -6 to 34deg. “13.5 deg” is middle of a GEM –Y-axis: Number of photons per events

Case 3: Mylar Shade (2.5cm) In (Integrated) Integrated over all the events –Significant decrease of photons! –Tail may come from electrons hit in edge

Case 3: Mylar Shade(2.5cm) In (phi-slicing) Trend kept, but overall decreasing

Case 3: Mylar shade(2.5cm) in (z-slicing) Trend kept (minimum at middle)..

Case 5: Mylar Shade(1cm) In (Integrated) Integrated over all the events –Peak position is same as 2.5cm shade –Width is much smaller!

Case 5: Mylar Shade(1cm) In (phi-slicing) Trend kept, but overall decreasing

Case 5: Mylar shade(1cm) in (z-slicing) Trend kept (minimum at middle)..

A Remark Geometrically, as long as ratio of spacing to height holds, loss is same It would be nice to check the width of photon distributions –It affects to rejection power