ME0 stack options – preview of a GMM talk

1. ME0 stack options – preview of a GMM talk • In Shashlik and CFCAL HE designs, space of Dz~30 cm exists behind 10 lambda for muons • 30 cm typically allows • 2 overlapping chambers, each of thickness 10 cm • plus 4+4 cm on each side for borated polyethylene and Pb shielding for neutrons • On the other hand, in HGCAL, a tail catcher of hadron showers is currently implemented as potentially dual purpose with ME0 muon detection • In fact this design is not being used for muon reconstruction yet • Some thoughts following conversations with Valeri Andreev, Roger R, Marcello M, Archana, Karl Gill, Alain Herve, Pawel…

2. High Rapidity Muon (HRM) layout • Proposed at ECFA workshop

3. Nose engineering drawing • Support of HE mechanical load and moment: Bolts at outer radius Sliding joint to strong back at inner radius

4. Current ME0 “stack” cartoons • Version A) Shashlik and CFCAL sims: 1x6 layer chambers, HE support from sliding joint to fixed-r conn. to strong back: requires ME0 inner, outer sections • Version B) HGCAL sim: 4x1 layer chambers, 0.47 l and 5.1 X0 between measurements 3.45 cm Brass absorber HE strong back - stainless Brass spacer ~10 cm 0.90 cm Brass absorber 3.45 cm 0.90 cm Brass spacer 2.5 borated polyethylene 1.2 Pb for n shielding ~4 cm … 34.8 cm ~36 cm 6-layer chambers 6-layer chambers ~8 cm ~8 cm ~4 cm muon

5. From Virdee Euroschool 2003… tail catching

6. Comments on versions A and B A (6-layer chambers): •  Pros • “Traditional” muon chamber design like CSC, DT • 6 muon layers versus 4 layers • Internal alignment is precise • Cost savings • Lots of space to bring ME0 services, cables •  Cons • Likely not a good HE calorimeter tail catcher • Mechanical support is more complicated B (single layer chambers) •  Pros • Good HE calorimeter tail catcher • Simple mechanical support •  Cons • 4 muon layers versus 6 layers • Alignment concerns • Increased cost • Almost no space for ME0 services except at outer periphery, extremely thin packages required

7. Other possibilities • Version C) 3x2 layer chambers, 0.54 l and 6.0 X0 between chamber measurements • Version D) 2x 3 layer chambers, 0.77 l and 8.6 X0 between chamber measurements Brass absorber 3.4 cm 4.5 cm 2-layer m Brass spacer 2.3 cm 4.0 cm Brass absorber 3.4 cm 2-layer m Brass spacer 2.3 cm 4.5 cm 34.2 cm … 4.0 cm 34 cm Brass absorber Brass absorber … Brass spacer Brass spacer 3-layer m 3-layer m Brass absorber Brass absorber Brass spacer Brass spacer 3-layer m 3-layer m

8. Comments on Versions C and D C (3 x 2layer chambers) •  Pros • Familiarity with 2-layer packages from GE1/1 etc • Pretty good HE tail catcher •  Cons • Thicker brass spacers – is it a mechanical problem? D (2 x 3layer chambers) •  Pros • Muon radiation isolation between successive chambers (more X0 in brass, is it enough?) • Fair HE tail catcher •  Cons • Unfamiliar package • Even thicker brass spacers – is it a mechanical problem?

9. Variant of ME0 stack that staggers 2-layer units • Version E) 2-layer units increases lever arm/pointing by a factor 2 • 2-layer units also convenient for construction (similar to GE1/1) • In Shashlik and CFCAL sims: 1x6 layer chambers 2-layer m 2-layer m 2-layer m 2-layer m 2-layer m 2-layer m HE strong back - stainless HE strong back - stainless ~10 cm ~10 cm 2.5 borated polyethylene 1.2 Pb for n shielding 2.5 borated polyethylene 1.2 Pb for n shielding ~4 cm ~4 cm 2-3.2 cm ~36 cm ~36 cm 6-layer chambers 6-layer chambers ~8 cm ~17 cm ~8 cm ~7 cm ~4 cm ~4 cm

10. Finally, ME0 segmentation • ME0 is used for muons to link to inner Tracker tracks • Especially at highest eta, Tracker uses endcap pixel disks • Error ellipse is therefore likely to be rather round • Pads, therefore, are better for matching than narrow strips • This also favors use as a tail catcher in a projective calorimeter • But ignores the possibility of modest rejection of low-Pt muon candidates • Skinny radial strips best for this • Studies are needed to identify the dominant effect?

11. Conclusions - suggestions • Verify the numbers, at least approximately • Try to install version A stack in HGCAL sim for now • HE: tail catcher capability doesn’t see to be high priority for studies, HGCAL group has expressed their flexibility • “Give” or at least “lend” the 34.8 cm space in z (and the cost) to the muon community for optimization • Z= 5193 – 5541 mm in present HGCAL (V.Andreev xml layout) • Later on, versions C (3 x 2layer HE-like) and E (staggered 3 x 2-layer muon units) look to be attractive alternatives for all HE choices

12. Backup slides

13. From the TDR of the HCAL

14. Behind the calculations • Brass density 8.4-8.73 (casting, rolling variations) • Composition 63% Cu and 37% Zn by weight • At 8.4, density of Cu=5.292 g/cm3, density of Zn 3.108 g/cm3 • At 8.73, reduce interaction and rad lengths by 3.93% • Interaction lengths, radiation lengths • Cu l=137.3 g/cm2, X0=12.86 g/cm2 • Zn l=138.5 g/cm2, X0=12.43 g/cm2 • Interactions add up weighted average of the r/l and r/X0 • For 63/37 brass, calculatel=16.4 cm, X0=1.511 cm

15. Valeri vs. my l calculations Valeri • 1.0 l for EE • 0.3 l for EE stainless back • 4.0 l for Si-brass • 4.15 l for Scint-brass • 9.45 l in front of GEM • 1.85 l for GEM-brass Me: • 1.0 l for EE (take as a given) • 0.3 l for EE stainless back • 3.9-4.07 l for Si-brass • 4.28-4.45 l for Scint-brass • 9.48-9.82 l in front of GEM (or 0.03-0.37l higher) • 1.90-1.98 l for GEM-brass

17. Stack cartoon ruler • (0, 5, 10, … cm)