中微子代写 ANY CALCULATOR Answer one question. If you answer more than one question, credit will only be given for the best answer.
Answer one question. If you answer more than one question, credit will only be given for the best answer.
Some data that may be useful for this question are listed at the end of each part.
Several radiochemical solar neutrino experiments have been proposed, following the Chlorine-Argon and Gallium-Germanium detectors. One such proposal was based on Iodine-127 (127I) nuclei absorbing electron neutrinos and changing into Xenon-127 (127Xe). The natural abundance of 127I is 100% and the half-life of 127Xe is 36 days.
i. Write down the corresponding reaction and draw a Feynman diagram for this process.
ii. Compute the minimum neutrino energy required for this reaction. Show your working.
iii. Based on your knowledge of radiochemical neutrino experiments, describe the general principles of the Iodine-Xenon experiment and the measurements that can be extracted. Compare the likely sensitivity for detecting solar neutrinos of an Iodine-based detector to those of the conventional Gallium and Chlorine detectors.[The masses of the 127I and 127Xe nuclei are 126.875394 and 126.875560 atomic mass units, respectively.]
Some particle physics experiments use Ring-Imaging Cherenkov (RICH) detectors to distinguish between different types of particles. A particular RICH detector is filled with CO2 gas, which has a refractive index n given by
n = 1 + (4.18 × 10−4) P ,
where P is the gas pressure at room temperature (measured in atmospheres). A beam composed of charged pions, charged kaons and protons passes through the chamber, each with a known momentum of 10 GeV/c.
i. List the main conditions for the Cherenkov effect and define the Cherenkov angle, θc.
ii. Calculate the minimum pressure required to observe pions, kaons and protons.
iii. The Cherenkov radiation is measured as a “ring” for each particle type. If the standard operating pressure is 3.8 atmospheres, calculate the values of θc for K± and π±. Comment on your result.
iv. Would this RICH detector (with a typical size of around 1 m3) be suitable for detecting neutrino interactions? Explain your reasoning.
The NOvA experiment is studying the disappearance of muon neutrinos, produced by an accelerator, over a distance of 810 km. The first oscillation maximum is found to be at an energy of 1.7 GeV.
i. Describe briefly the concept of neutrino oscillations and explain the fundamental parameters associated with this phenomenon.
ii. Assuming two-flavour oscillations in vacuum, what is the corresponding value of the parameter ∆m2?
iii. What neutrino energy corresponds to the third oscillation maximum?
iv. NOvA measured two possible values of sin2θ:
sin2θ = 0.4 or sin2θ = 0.6.
Explain this result.
What is the νµ survival probability at the second oscillation maximum?
The SNO experiment was designed to detect solar neutrinos in 1000 tonnes of heavy water (D2O). One phase of the SNO experiment ran for 391 live days. During that time it recorded 2180 charged current (CC) interactions and 2010 neutral current (NC) interactions of solar neutrinos with deuterons.
i. Assume that Cherenkov radiation is always detected while the neutron capture process is only 50% efficient. The values of CC and NC crosssections are
σ(CC) = 6 × 10−43 cm2;
σ(NC) = 4 × 10−43 cm2,
and the molar mass of D2O is 20g.
Compute the total neutrino CC and NC fluxes.
ii. Calculate the fraction of electron neutrinos from the Sun that areobserved as other flavours in SNO.