A gentle introduction

Due to the electric charge, they continuously interact with the electrons in the medium Neutral particles. When we express dE/dx as a function of particle momentum (p=mv, so we change the particle velocity, v, with p/m), we add a dependence on mass that can allow us to distinguish between different particles at low temperatures. . Graph of the braking force along the track of a particle: the Bragg curve. Most energy is lost at the end of the track: the Bragg peak.

When the electron is deflected from the nucleus by the electric field, it emits a photon. The radiation length (X0) is the characteristic length that describes the energy decay of a beam of electrons:. independent of material when thickness expressed in terms of X0:. This relationship becomes complicated for relativistic particles due to the wandering of energetic knock-on electrons whose range exceeds the dimensions of the fiducial volume.

For a qualitative assessment of the nonlocality of energy deposition in different media by such modestly energetic electrons, see Ref. Here p, βc and z are the momentum, velocity and charge number of the incident particle, and x/X0 is the thickness of the scattering medium at the radiation length (defined below). 30.15) describes scattering from a single material, whereas the usual problem involves multiple scattering of a particle traversing many different layers and mixtures.

Cherenkov Radiation

Introduction

Motion in Magnetic Field

The Helix Equation

Unlike charged particles, which continuously deposit energy due to ionization, photons usually suffer from one-time interactions that produce charged particles. Electromagnetic cascades such as pair production and bremsstrahlung create more electrons and lower energy photons. Excitation of individual atoms to produce electron-‐ion pairs in gas detectors, a pair of electron-‐hole pairs in semiconductor detectors.

Cloud Chamber

Wilson  Cloud  chamber  1911

The ionization of the particle and its behavior in passing through the foil is the same as that of an electron, but it turns to the wrong side.

Nuclear Emulsion

A results analog of the cloud chamber can be obtained with a picture 1000x smaller (emulsion density is about 1000x greater than gas at 1 atm). Due to the greater 'stopping power' of the emulsion, particle damage could be observed more easily. A results equivalent to the cloud chamber can be obtained with a picture 1000x smaller (emulsion density is about 1000x greater than gas at 1 atm).

Discovered in the 1930s, the muon was first thought to be the Yukawa meson that mediates the strong force.

Bubble Chamber

It was therefore not useful for cosmic ray physics, but which in the 50s moved particle physics to accelerators. Unlike cloud chambers, bubble chambers could not be triggered: the chamber must be in a superheated state when the particle arrives. In the bubble chamber, with a density about 1000 times greater than the cloud chamber, the liquid acts as the target and the detection medium.

A negative 1300 MeV pion hits a proton and produces a neutral kaon and a °, which decays into a ° and a photon. A negative pion of 1300 MeV hits a proton and produces a neutral kaon and a Ʃ°, which decays into a Λ° and a photon.

The  Big  European  Bubble  Chamber

The excellent position resolution (5 µm) and the fact that target and detection element are the same (in the H-chambers) make the Bubble Chamber unbeatable for the reconstruction of complex decay modes.

LOGIC and

ELECTRONICS

Early  Days  of  ‘Logic  Detectors’

Geiger Rutherford

Detector + Electronics 1929

While Sir Samuel Curran was working in Berkeley, USA on the Manhattan Project in 1944, he needed a better method to detect small amounts of uranium. The "N" of gases changes with pressure, so it's kind of like a knob to change the momentum or mass thresholds. I Please note that the final detector consists of the following order: two Cerenkov counters and a final scintillator.

I Strong evidence for antimatter comes from the observation of interaction, where released energy greater than the mass of a particle.

Spark Counters

The multi-wire proportional chamber was a real breakthrough that earned the Nobel Prize in Physics in 1992. The electrons drift towards the wires in the electric field and begin to move around a.

MWPC and Drift Chambers

Electromagnetic  Showers

Hadronic showers

Z-Discovery at UA1/UA2 1983

They made it possible to restore the 'image' that the Bubble Chambers had created until the end of the 1960s. When the particle traverses the volume, ions drift towards the cathode and electrons towards the anode. Detectors with long drift distances perpendicular to a readout plane provide three-dimensional information, one of which is the time projection.

A (typically strong) magnetic field parallel to the driving direction suppresses transverse diffusion (σ = √ with a factor 2Dt). Multiple measurements of energy deposition along the particle trajectory combined with the measurement of momentum in the magnetic field allow excellent particle identification [91], as can be seen in Fig. The electrons reach a Fermi plateau value of 1.4 times the most likely energy drop at minimum ionization.

Muons from pion decays are separated from pions at low momentum; π/K separate at all moments except in the crossover region.

Particle IDentification

Working Principle of a Silicon Tracking Device

Due to the Landau fluctuations and the most likely signal of 22,500 electron-hole pairs, the most likely collected charge is therefore 22500 holes or 9 electrons collected on each side of the detector, corresponding to 3.6 fC. The generated holes drift along the electric field created by the bias to the P+N doped strips10 while the electrons drift to the n+ backplane. The charges collected on the doped strips are then induced by capacitive coupling to the aluminum readout strips, which are directly connected11 to the readout chip's charge preamplifier.

Electron-hole pairs resulting from the ionization of the crossing charged particle, according to the Bethe-Bloch formula, move to the electrodes on the sensor surfaces. The segmentation in the pn junctions allows the charges to be collected on a small number of strips, where they connect capacitively to the Al readout strips. This is then connected to the readout electronics, where the intrinsic signal is formed and amplified.

In the case of segmented p-strip implants in an n-bulk silicon material, holes are collected at the p+strips. 9 In the most common p-in-n sensor, holes are collected on the segmented side, but for n-in-p, n-in-n or double-sided sensors, electrons are also collected. The photo shows a rare view during construction, with all the modules in hand and three layers of the barrel detector assembled.

The impact parameter d0 is defined by the shortest distance between a reconstructed trajectory and the primary vertex, it is a decisive quality parameter of the full detector performance. Each hybrid reads out two detectors with the chain strips connected to each other and to the amplifiers by wire bonding. The upper part of the figure shows the different track points of the three detector planes together with the reconstructed tracks.

The lower part, an exploded view, shows the ability to interpolate the trace down to the primary point and resolve the secondary point b. Graph (2) demonstrates the clear dominance of lifetime measurement b with the introduction of node detectors at LEP. The lower part, an exploded view, shows the ability to interpolate the trace to the primary point and resolve the secondary point b.

Tracking Provides: momentum Tracking Provides: momentum

Tracking provides: Global objectsTracking provides: Global objects

Visualizing particle trajectoriesVisualizing particle trajectories

The  choice  of  the  magnet  system…

The  reason  behind  the  choice

Signal processing for track ftting: hitsSignal processing for track ftting: hits

Signal Processing for Track Fitting: Kicks Signal Processing for Track Fitting: Kicks Signal Processing for Track Fitting: Kicks.

Momentum Measurement

The  Trajectory  is  an  helix

The  rule  of  the  game:  measure  R  with  highest  accuracy What  we  really  measure  is  the  sagitta

Multiple  Coulomb  Scattering

Ionization  Energy  Loss

Effects of ComplicationsEffects of Complications

Both  effects  decrease  with  p T

Since track reconstruction is performed independently in ID and MS, the reconstruction efficiency for CB or ST muons is the product of the muon reconstruction efficiency in ID, the reconstruction efficiency in MS, and the matching efficiency between ID and MS measurements (which includes the reassembly efficiency in the case of chain 2). It is therefore possible to study the full reconstruction efficiency by measuring these individual contributions. A tag-and-probe method is used which is sensitive to either the ID efficiency or the combined MS and matching efficiency.2 This technique is applied to samples of dimuons from the J/ψ and Z decays.

For Z → µ+µ− decays, events are selected by requiring two oppositely charged isolated tracks with a dimuon-invariant mass near the mass of the Z boson. One of the tracks is required to be a CB muon candidate and to have triggered readout of the event (see Section 6). If the MS reconstruction and matching efficiency are to be measured, the probe must be an ID trace.

2 Efficiencies determined by the mark-and-probe method and an alternative method based on Monte Carlo generator-level information were found to agree within statistical uncertainty [1, p. 221], which also shows that possible correlations between tag and probe muons are negligible. 3 Invariant mass, m, distribution of pairs of muon labels (chain 2) and probe ID tracks for different sets of muon isolation requirements for the Z boson analysis, as indicated in the legend.

The presence of backgrounds in the data leads to an apparent decrease in the muon efficiency in the range pT. To investigate the reconstruction efficiency at lower transverse momenta, dimuon pairs from J/ψ → µ+µ− decay are used in the same way as those from Z → µ+µ− decay. In this case, the invariant mass distribution of the tag and probe pairs is fitted using the sum of a quadratic background term and a Gaussian signal term [5].

The invariant mass spectra are shown for tag-and-probe pairs in which the probes are coupled to reconstructed muons (see Section 6.5) and for mismatched tag-and-probe pairs. The muon reconstruction efficiency is then extracted from a simultaneous fit to the distributions obtained from the matched and mismatched tag-and-probe pairs. For the efficiency measurements in the pT > 20 GeV region, five million Z → µ+µ− events were simulated with PYTHIA 6.4 [6], which went through the full simulation of the ATLAS detector.