Calorimetry: Energy Measurements

2758 days ago, 751 views
PowerPoint PPT Presentation

Presentation Transcript

Slide 1

Calorimetry: Energy Measurements Measuring particles' energies through Electromagnetic and Hadronic associations Prof. Robin D. Erbacher University of California, Davis References : R. Fernow, Introduction to Experimental Particle Physics, Ch. 11 D. Green , The Physics of Particle Detectors, Ch. 11, 12 K. Kleinknecht, Ch. 6

Slide 2

Introduction Energy of a molecule or gathering of particles is fundamentally measured damagingly. We should totally stop the molecule in our finders to quantify its full vitality. The vitality is saved in a limited space, so position can be resolved with precision reliant on transverse vitality changes and indicator plan. Exactness of vitality estimation originates from a: Constant expression: Uniformity of the identifier medium, and a Stochastic expression: Level of dynamic testing wrt add up to finder volume Calorimetry can hence give energy of a molecule needlessly to the inward following estimations, valuable in tidying up foundations.

Slide 3

Multipurpose Calorimeters Calorimeter utilize far reaching, has turned out to be practically key. Nonpartisan particles (  s , neutrons) are just identified by this. Why? Inspecting calorimeters are now and then utilized as  finders. Triggers for planes: as impact energies increment, molecule assortment increments, and we get exceptionally collimated splashes of optional particles in a restricted precise dispersions. Can be made secluded, and to cover expansive strong points. Measure scales as ln(E), yet B-field following goes like E 1/2 .

Slide 4

Partons  Particles  Jets Processes making planes are extremely confounded, and comprise of parton discontinuity, then both electromagnetic and hadronic giving in the locator. Recreating planes is, normally, likewise exceptionally troublesome. Fly vitality scale and recreation is one of the biggest wellsprings of efficient mistake. More on Jets on Monday!

Slide 5

Electron and  ��  Interactions At E > 10 MeV, communications of  s and e - s in matter is commanded by e + e - match generation and Bremsstrahlung. At lower energies, Ionization gets to be critical. The proportion of the vitality misfortune for these procedures is: Critical Energy: When vitality misfortune because of Brem and vitality misfortune because of ionization are =.

Slide 6

Electromagnetic Showers A substituting arrangement of collaborations prompts to a course: Primary  with E 0 vitality match produces with 54% likelihood in layer X 0 thick by and large, each has E 0/2 vitality If E 0/2 > E c , they lose vitality by Brem Next layer X 0 , charged molecule vitality declines to E 0/(2e) Brem of avg vitality between E 0/(2e) and E 0/2 is transmitted Mean # particles after layer 2X 0 is ~4 Radiated  s combine create again Cloud chamber photograph of electromagnetic course between dispersed lead plates. After n eras (dx= nX 0 ), 2 n particles, avg vitality E 0/2 n for shower. Course stops: e - vitality  basic vitality E c = E 0/2 n . Number of eras: n=ln(E 0/E c )/ln 2 . Number of particles at shower most extreme : N p = 2 n = E 0/E c .

Slide 7

EM Shower Properties Typical properties of electromagnetic showers: # particles at shower most extreme N p corresponding to E 0 Track length (profundity) of e - and e + relative to E 0 Depth for greatest X max increments logarithmically: Longitudinal vitality testimony: Transverse shower measurement: different disseminating of low vitality e - : Moliere Radius: Radial conveyance in R M free of material utilized! 99% of vitality is inside a range of 3 R M . Longitudinal vitality statement for e - in lead, fit to gamma work

Slide 8

Energy Resolution Energy determination of perfect identifier of endless measurements is constrained by factual vacillations. Case: For E c =11.8 MeV and identification cut-off E k =0.5 MeV and a track length of 176 cm/GeV, best determination ~ Losses of Resolution : Shower not contained in locator  change of spillage vitality; longitudinal misfortunes are more regrettable than transverse spillage. Factual vacillations in number of photoelectrons saw in identifier. On the off chance that is # photoelectrons per unit essential molecule E, Sampling vacillations if the counter is layered with idle safeguard. On the off chance that dynamic region is gas or fluid argon, low e-move everywhere points from the shower pivot, Landau tail prompts to "way length vacillations".

Slide 9

Electromagnetic Calorimeter Types Homogeneous "shower counters": Best execution from natural shining precious stones . Case of NaI(Tl) have accomplished ~ . Additionally utilize lead glass, identifies Cerenkov light of electrons, constrained by photoelectron measurements. Inspecting calorimeters: Layers of idle safeguard, (for example, Pb) substituting with dynamic indicator layers, for example, scintillator or fluid. Resolutions ~7%/E or somewhere in the vicinity. Fluid honorable gasses: Counters in view of fluid respectable gasses (with lead plates, for instance) can go about as ionization chambers. L Ar - Pb forms get ~10%/E . Ionization read out by cathodes appended to plates (no PMTs!). Inconvenience: moderate accumulation times (~1  s). Varieties in the 1990s: "Accordion" for quick readout (front/back readout) and L Kr homogeneous indicator (energy&time determination).

Slide 10

Electromagnetic Calorimeter Types "lead-scintillator sandwich" calorimeter intriguing precious stones (BGO, PbW, ...) fluid argon calorimeter Δ E/E ~ 18%/√E Energy resolutions: Δ E/E ~ 20%/√E Δ E/E ~ 1%/√E

Slide 11

Hadron Calorimeters When an unequivocally associating molecule above 5 GeV enters matter, both inelastic and versatile scrambling amongst particles and nucleons happen. Auxiliary hadrons  cases: ��  and K mesons, p and n. Vitality from essential goes to optional, then tertiary, and so on. Course just stops when hadron energies sufficiently little to stop by ionization vitality misfortune or atomic assimilation. Hadronic Shower: spatial scale for shower improvement given by atomic assimilation length   . Look at X0 for high-Z materials, we see that the size required for hadron calorimeters is huge contrasted with EM calorimeters.

Slide 12

Compensating Calorimeters Improvements in vitality determination can be accomplished if showers initiated by electrons and hadrons of same vitality deliver same noticeable vitality (identifier reaction). Requires the misfortunes to be "adjusted" somehow. Three strategies: Energy lost by atomic responses compensated for by splitting of 238 U, freeing n and delicate  beams. Can get reaction near equivalent: proton-rich finder em shower diminishes, had shower increments because of more atomic responses. On the off chance that have heaps of H2, remuneration accomplished with high safeguard material: in inelastic crash of hadrons w/safeguard cores, neutrons are created  pull back protons, bigger flag. Diminish variance in EM segment: weight singular counter reactions, and even reaction out in all cases.

Slide 13

CDF Sampling calorimeter is orchestrated in projective "towers" indicating at the cooperation area a large portion of the profundity is for the hadronic part of the calorimeter

Slide 14

CMS Hadron Calorimeter

Slide 15

Not Covered Shower shapes in hadron calorimeters Fluctuations in hadronic vitality estimations Position determination in the calorimeters Shower most extreme indicators New calorimeter outlines for ILC with silicon, following for "molecule stream" calculations. Next Monday, Guest Lecture : Calibrating em and hadron calorimeters, remaking planes, deciding the fly vitality scale. (Getting from calorimetry to material science comes about!) Up next… Prof. Conway, measurements and information investigation

Slide 16

Example of Gaussian Distribution Single hit "lingering" in silicon strip indicator (separate from hit to known track position):

Slide 17

Example of Binomial Statistics CDF track trigger proficiency:

Slide 18

Poisson Process Plot of watched tau lepton match mass appropriation in CDF: (Sorry, no Higgs yet… ) Note distinction amongst straight and log scales!

Slide 19

The Higgs  2 The most renowned plot in high vitality material science… Tells us the Higgs is close!

Slide 20

Complicated Confidence Interval All the world's information about the CKM grid…