The Importance of High-Precision Hadronic Calorimetry to Physics

Transcription

1 The Importance of High-Precision Hadronic Calorimetry to Physics John Hauptman, Iowa State University IAS Program in High Energy Physics The Hong Kong University of Science and Technology 4-30 January 2016 Outline: Isn t this just some technical stuff? Yes, it is very technical and you practically have to be a nuclear physicist to get it right. What we know and how we know it. The standard model particles, most of which required high-precision detectors or accelerators for their discovery. Measuring hadronic particles (e.g., quark and gluon jets) with high precision is the last experimental challenge for big detectors Large volume tracking and high-precision vertex chambers exist in many big detectors today. Magnetic field volumes at 4T are challenging but exist. How to get there Calorimetry is difficult and expensive ( the low point of my life ) and there are currently two widely different technical paths: particle-flow calorimetry and dual-readout calorimetry. You pays your money and you takes your choice One of the beauties of a circular electron collider is there can be 2, 4 or even 6 interaction regions with very different detector technologies represented, like happened at PEP/SLAC and at LEP/CERN. 1

2 Scientific goal is to measure every particle of the SM with comparable precision ~2% 2

3 Anderson s high-precision cloud chamber photograph: Simultaneously, the discovery of the positron and demonstration of the existence of anti-matter. 3

4 How to miss discovering charm: have a detector with too much multiple scattering after the target 4

5 What precision buys you: an obvious signal with only 250 events. 25 events would have been enough. 5

6 The story at SPEAR/SLAC was similar, although it was the precision of the machine s beam energy that counted. Beam energy 6

7 Discovery of the Upsilon, bottom quark bound state, in the di-muon channel. 7

8 W and Z 8

9 The discoveries made at hadron machines are ultimately measured with high precision at electron machines: note however, that the mass precision in most cases comes from the machines, not the detectors. 9

10 fundamental (sm) particle or c detector composite (of quarks) W ±! all q q and ` ` sm 0.1 F Z 0! all q q and ` ` sm 0.1 F t! W + b sm 1.0 F g! u, d, s sm 10 F measure only u, d (q)! s sm (quark) 10 F decay products s! K s sm (quark) 10 F c! D s sm (quark) 10 F b! B s sm (quark) 10 F 0! composite (u, d) 25 nm measure only decay s ± sm (lepton) 87 µm D 0 composite (c) 124 µm D ± composite (c) 315 µm vertex B 0 composite (b) 464 µm detector B ± composite (b) 496 µm KS 0! composite (s) 27 mm! N composite (s) 79 mm tracking ±, 0,. composite (s) mm detector K ± composite (s) 3.7 m ± composite(u, d) 7.8 m KL 0 composite (s) 15.5 m µ ± sm (lepton) 10 6 m tracking and n composite (u, d) m calorimetry p composite (u, d) 1 e ± sm (lepton) 1 e, µ, sm (lepton) 1 sm 1 Table 1: All particles of interest for a detector, ordered by their decay length, c, inconvenientunits. 10

11 The best-in-theworld hadronic W-->jj mass (so far?) from ATLAS. You might think you see Z-->jj 11

12 p/p [ 8 s 0.3BL 2 ]p s is sagitta measurement E/E k/ p E Number of shower particles is N / E and is Poisson. E / p N / p E. k depends on construction 12

13 Why is hadronic energy measurement so difficult? 13

14 Emulsion measurement of 30 GeV proton breaking up a nucleus: this is what happens throughout a calorimeter volume 14

15 15

16 16

17 17

18 Essentially, all electron showers look the same. 18

19 19

20 20

21 This is the W and Z di-jet mass distribution you get from an excellent hadronic calorimeter: E E 30% p E These events are actually taken from CERN test beam data of the DREAM module at beam energies of 50, 100, and 200 GeV. Leakage fluctuations were suppressed using the beam momentum, and therefore these data only indirectly represent a calorimeter with a 30% stochastic term 21

22 Yunyong Wang, Beijing U. One ton of copper Twenty tons of lead 22

23 Do we think this is possible? DREAM data (leakage suppress using beam energy) /E 30%/ p E GEANT simulation, HP means high precision which means /E 32%/ p E the neutrons were treated more properly 23

24 50 GeV /E 4.36% 80 GeV /E 3.50% 24

25 90 GeV /E 3.36% 100 GeV /E 3.21% 25

26 200 GeV /E 2.45% (! 2.21%) Note well: (1) all of these response functions are Gaussian (2) no correction for leaked neutrons, etc. (3) simple direct dual-readout 26

27 Dual-readout is close to achieving (in geant high-precision simulation) /E 30%/ p E Next step for us: built and test alarge(4t)coppermoduletotestthis. 27

28 What does a 30% stochastic resolution buy? e + e! t t! 6-jets M GeV/c 2 hmsum Entries Mean RMS χ / ndf / 173 nevents ± m ± σ ± pol ± pol ± pol ± pol e-05 ± e Mass, GeV 28

29 hh_0 Entries 8106 Mean RMS χ / ndf / 48 Prob p ± 83.8 p ± 0.1 p ± p ± 10.0 p ± 0.13 p ± p ± M Higgs, GeV/c e + e! Z 0 H! jj + c c M GeV/c 2 Counts Background e e ZZ / WW / Bhabha Signal e e HZ e e X Signal + Background Mean 121 χ 2 / ndf / 80 Entries 500 Constant ± Mean M ± 0.06 H σ ± M H hall β ± κ ± bkg p ± bkg p ± bkg p ± e + e! Z 0 H! e + e + X Missing mass against the Z 0! e + e GeV/c 29

30 200 GeV GEANT/DREAM 200 GeV hadronic shower DREAM W & Z M/M 2.5% E/E 2.3% 30

31 The energy resolution of an excellent hadronic calorimeter is E E 30% p E and a sampling electromagnetic calorimeter is about a factor of 3 better. The momentum resolution of a very good tracking system is p p p(gev/c) Therefore, the resolutions for em, hadronic, and charged particles are E,p e ± / ± /h j/g µ ± % 10% 10% 0.1% % 3.0% 3.0% 1.0% % 1.5% 1.5% 10% 31

32 Unification of experimental resolutions for all the partons of the Standard Model 32

33 This unification of experimental resolutions in energy and momentum near the 2% level means that you don t need to care about the theoretical speculations Andrew Cohen on a putative 1.9 TeV vector boson: decays to γγ, WZ,... jets,em JoAnne Hewitt on Left-Right signatures: decays to WZ,... jets,em Tom Rizzo on pmssm supersymmetry: decays to γγ, WZ,... jets,em Other than extreme exotics, all conceivable theoretical proposals will always end up in the detector as W, Z, γ, t, or gluon and be reconstructed with comparable four-vector resolutions. That s why we think high-precision hadronic calorimetry is vital in at least one detector at the the next electron collider. 33

34 There s more to a detector than calorimeters: Overall event efficiency (high Br s) Momentum, p (tracking chambers) Magnetic field, B (superconducting) Lifetime, λ = γβcτ (vertex chamber) 34

35 Most of the W,Z branching ratios are in hadronic decays Br(Z! q q) 20 Br(Z! e + e ) 70% 3.4% Br(W! q q) 67% are reconstructable as four-vectors, vs. W! ` For WW,WZ, and ZZ final states, the rates 100 s 35

36 More ideas for a new technology detector: an 8 Tesla bending field. 36

37 Alexander Mikhailichenko, LNS Cornell University No iron, no fringe field, no forces. Very uniform tracking B-field volume. Leaves detector volume open for future additions. 37

38 Thank you 38

39 Spares 39

40 40

41 41