ME0 stack options

1. ME0 stack options • In Shashlik and CFCAL HE designs, space of Dz~36 cm exists behind 10 lambda for muons • An ideal ME0 detector geometry has been inserted and is being used for simple muon studies • 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 • Baseline proposed at ECFA workshop Oct. 2013 • ME0 covers eta 2.0 to as high as possible (<4.0) within endcap

3. Nose engineering drawing • Support of HE mechanical load and moment: Bolts at outer radius Services & Support Transfer load from HE over ME0 chambers here Sliding joint to strong back at inner radius

4. GEM chamber thickness • Current GE1/1 design: • 44mm for each layer includes electronics, services • 88mm for 2 layers – too thick for ME0 6 layers • Short (high-eta) ME0 design allows for central readout board • Try for 50mm or thinner for 2 layers

5. Simulation ME0 “stack” cartoons • Version A) Shashlik and CFCAL sims: • 6x1 layer chambers, no segmentation in phi (ideal but unfeasible in reality) • Version B) HGCAL sim: • 4x1 layer chambers, 0.47 l and 5.1 X0 between measurements • HE tail catcher between 9.5-11 l 2.5 borated polyethylene 1.2 Pb for n shielding ~4 cm 3.45 cm Brass absorber Brass spacer 0.90 cm 1-layer, 2*p chambers Brass absorber 3.45 cm 0.90 cm Brass spacer … 34.8 cm ~36 cm? ~23 cm ~4 cm muon

6. ME0 version A (Shashlik, CFCAL)

7. From Virdee Euroschool 2003… tail catching

8. Variant of ME0 stack that staggers 2-layer units • Cartoon rotated to match the orientation of engineering drawings • Version C) 2-layer units convenient for construction (similar to GE1/1) • 20-degrees/chamber in phi, 2-chamber units offset by 6.67 degrees • Assures 4 or more hits at all f , given the dead space between abutting chambers • Absorber in between (4 cm) improves tail catcher function etc.→ etc.→ etc.→ 2.5 borated polyethylene plus 1.2 Pb for n shielding 2.5 borated polyethylene plus 1.2 Pb for n shielding Absorber f direction → Dz = 35 cm mchamber 4 cm 4 cm 9 cm 9 cm 9 cm

9. 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 • Squarish 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?

10. Conclusions - suggestions • Should install version A stack in HGCAL sim ASAP • 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 to the muon community for optimization • Z= 5193 – 5541 mm in present HGCAL (V.Andreev layout) • Expect more detailed discussion at GMM in 2 weeks

11. Backup slides

12. Variant of ME0 stack that staggers 2-layer units • Version C) 2-layer units convenient for construction (similar to GE1/1) • 20-degrees/chamber in phi, 2-chamber units offset by 6.67 degrees 2.5 borated polyethylene 1.2 Pb for n shielding 2.5 borated polyethylene 1.2 Pb for n shielding 4 cm Spacer/ absorber Spacer/ absorber etc.→ Spacer/ absorber Spacer/ absorber etc.→ Dz = 35 cm Spacer/ absorber Spacer/ absorber etc.→ 9 cm 2-layer m , 20-degrees 2-layer m , 20-degrees 2-layer m , 20-degrees 2-layer m , 20-degrees 2-layer m , 20-degrees 2-layer m , 20-degrees 2-layer m , 20-degrees 2-layer m , 20-degrees Spacer/ absorber Spacer/ absorber 4 cm f direction →

13. From the TDR of the HCAL

14. Other possibilities • Version D) 3x2 layer chambers, 0.54 l and 6.0 X0 between chamber measurements • Version E) 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

15. Comments on Versions D and E D (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? E (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?

16. 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

17. 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

19. Stack cartoon ruler • (0, 5, 10, … cm) 40 35 30 25 20 15 10 5 0