6. Build your own collider detector [4pts] You have at your disposal the followi

Question

6. Build your own collider detector [4pts] You have at your disposal the following pieces of detectors to build a high energy collider experiment. Number the pieces you would need, form inner-most (closest to the collision point) as #1 to outer-most (furthest from the collision point). Not all pieces need to be used but any given piece can be used multiple times. Then write a couple of sentences about what each part of the detector is useful for (e.g. which type of particles can it measure and what kinematic property does it measure). a. silicon-based vertex detector b. electromagnetic calorimeter c. hadronic calorimeter d. bubble chamber e. tracking detector inside a magnetic field

Explanation / Answer

Silicon based vertex detector: Most silicon particle detectors work, in principle, by doping narrow (usually around 100 micrometers wide) strips of silicon to turn them into diodes, which are then reverse biased. As charged particles pass through these strips, they cause small ionization currents that can be detected and measured. Arranging thousands of these detectors around a collision point in a particle accelerator can yield an accurate picture of what paths particles take.

Electromagnetic calorimeter: An electromagnetic calorimeter is one specifically designed to measure the energy of particles that interact primarily via the electromagnetic interaction. The response of a calorimeter can be described in terms of the e/h ratio. This is the measure of how well a calorimeter responds to leptons or photons versus hadrons. Ideally one would want a ratio e/h~1, this condition is called compensation.

Hadronic calorimeter: The Hadron Calorimeter (HCAL) measures the energy of “hadrons”, particles made of quarks and gluons (for example protons, neutrons, pions and kaons). Additionally it provides indirect measurement of the presence of non-interacting, uncharged particles such as neutrinos. The HCAL is a sampling calorimeter [see explanation below] meaning it finds a particle’s position, energy and arrival time using alternating layers of “absorber” and fluorescent “scintillator” materials that produce a rapid light pulse when the particle passes through. Special optic fibres collect up this light and feed it into readout boxes where photodetectors amplify the signal.

Bubble chamber: A bubble chamber is a vessel filled with a superheated transparent liquid (most often liquid hydrogen) used to detect electrically charged particles moving through it. The bubble chamber is similar to a cloud chamber, both in application and in basic principle. It is normally made by filling a large cylinder with a liquid heated to just below its boiling point. As particles enter the chamber, a piston suddenly decreases its pressure, and the liquid enters into a superheated, metastable phase. Charged particles create an ionization track, around which the liquid vaporizes, forming microscopic bubbles. Bubble density around a track is proportional to a particle's energy loss.

Tracking detector inside a magnetic field: Unlike tracking and calorimetry, the magnet doesn't detect the particles directly—it affects them in revealing ways. Magnetic fields curve the paths of charged particles, and the direction of curvature depends on whether the particle is positively or negatively charged. Thus, a tracking system with a magnetic field can distinguish between matter and antimatter. In addition, the deflection is larger for slow, low-momentum particles than it is for fast, high-momentum ones. Fast particles zip right through while slow ones loop around, possibly several times.

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