Conceptual introduction to quantum mechanics: some keys ideas

Grao en FísicaPódese consultar a versión en castelán en: http://hdl.handle.net/10347/12470[EN]The course work presented here is a mathematically precise introduction to the conceptual body, and calculation tools, of Quantum Mechanics, as a basis for the study of Quantum Physics. It is addressed to those that, having a mathematical background in differential and integral calculus, and being familiar with Classical Mechanics and waves, would like to have an insight into the foundations of Quantum Mechanics, and acquire in a short period of time the power of calculation to resolve physical problems in this field. In particular, to students following a course of Quantum Physics in a graduate program, either in Science or Engineering. Feynman's propagation is used as an axiomatic basis for Quantum Mechanics, completed with the generally admitted ideas about the measurement problem. A simple notion is provided of the immersion that Quantum Mechanics undergoes in Quantum Field Theory, illustrated with the emission of quanta. This course has been conducted at the University of Santiago de Compostela in recent years, as part of the graduate program in Physics. It is continued with a second part containing the analytic resolution of a number of normalized cases of the Schrödinger equation, within the subject of Quantum Physics I.[ES]El material didáctico que se presenta aquí es una introducción, matemáticamente precisa, al cuerpo conceptual y herramientas de cálculo de la Mecánica Cuántica, como base para el estudio de la Física Cuántica. Está dirigido a personas que, teniendo una base matemática en el cálculo diferencial e integral, y estando familiarizados con la Mecánica Clásica y las ondas, deseen conocer de cerca los fundamentos de la Mecánica Cuántica, y adquirir en poco tiempo capacidad operativa para la resolución de problemas físicos en esta disciplina. En particular, a alumnos que cursen una asignatura de Física Cuántica, en cualquier programa universitario, ya sea en Ciencias o Ingeniería. Se utiliza la propagación de Feynman como base axiomática de la Mecánica Cuántica, completada con las ideas generalmente admitidas sobre el problema de la medida. Se proporciona una idea simple de la inmersión que sufre dicha Mecánica Cuántica en la Teoría Cuántica de Campos, ilustrado con la emisión de cuanta. Este curso se ha llevado a cabo durante los últimos años en la Universidad de Santiago de Compostela, dentro del programa de grado en Física, y se continúa con la resolución analítica de una serie de casos normalizados de la ecuación de Schrödinger, como parte de la asignatura de Física Cuántica I

Evidence for the decay B0S→K¯∗0μ+μ−

A search for the decay B0S→K¯¯∗0μ+μ−BS0→K¯∗0μ+μ− is presented using data sets corresponding to 1.0, 2.0 and 1.6 fb−1 of integrated luminosity collected during pp collisions with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations. The branching fraction of the B0S→K¯¯∗0μ+μ−BS0→K¯∗0μ+μ− decay is determined to be B(B0s→K¯¯∗0μ+μ−)=[2.9±1.0(stat)±0.2(syst)±0.3(norm)]×10−8B(Bs0→K¯∗0μ+μ−)=[2.9±1.0(stat)±0.2(syst)±0.3(norm)]×10−8, where the first and second uncertainties are statistical and systematic, respectively. The third uncertainty is due to limited knowledge of external parameters used to normalise the branching fraction measurement

Measurement of ϒ production in pp collisions at √ s =13 TeV

The production cross-sections of ϒ(1S), ϒ(2S) and ϒ(3S) mesons in proton-proton collisions at s√=13s=13 TeV are measured with a data sample corresponding to an integrated luminosity of 277 ± 11 pb−1 recorded by the LHCb experiment in 2015. The ϒ mesons are reconstructed in the decay mode ϒ → μ+μ−. The differential production cross-sections times the dimuon branching fractions are measured as a function of the ϒ transverse momentum, pT, and rapidity, y, over the range 0 < pT < 30 GeV/c and 2.0 < y < 4.5. The ratios of the cross-sections with respect to the LHCb measurement at s√=8s=8 TeV are also determined. The measurements are compared with theoretical predictions based on NRQCD

Observation of the decay Λ b 0 → ψ(2S)pπ−

The Cabibbo-suppressed decay Λ b 0  → ψ(2S)pπ− is observed for the first time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9 fb−1 of integrated luminosity at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The ψ(2S) mesons are reconstructed in the μ+μ− final state. The branching fraction with respect to that of the Λ b 0  → ψ(2S)pK− decay mode is measured to beB(Λ0b→ψ(2S)pπ−)B(Λ0b→ψ(2S)pK−)=(11.4±1.3±0.2)%,B(Λb0→ψ(2S)pπ−)B(Λb0→ψ(2S)pK−)=(11.4±1.3±0.2)%,where the first uncertainty is statistical and the second is systematic. The ψ(2S)p and ψ(2S)π−mass spectra are investigated and no evidence for exotic resonances is found

Measurement of Angular and CP Asymmetries in D0→π+π−μ+μ− and D0→K+K−μ+μ− Decays

The first measurements of the forward-backward asymmetry of the dimuon pair (AFB), the triple-product asymmetry (A2ϕ), and the charge-parity-conjugation asymmetry (ACP), in D0→π+π−μ+μ−and D0→K+K−μ+μ− decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5  fb−1. The asymmetries are measured to be AFB(D0→π+π−μ+μ−)=(3.3±3.7±0.6)%, A2ϕ(D0→π+π−μ+μ−)=(−0.6±3.7±0.6)%, ACP(D0→π+π−μ+μ−)=(4.9±3.8±0.7)%, AFB(D0→K+K−μ+μ−)=(0±11±2)%, A2ϕ(D0→K+K−μ+μ−)=(9±11±1)%, ACP(D0→K+K−μ+μ−)=(0±11±2)%, where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the standard model predictions

Measurement of the Lifetime of the Doubly Charmed Baryon Ξ++cc

The first measurement of the lifetime of the doubly charmed baryon Ξ++cc is presented, with the signal reconstructed in the final state Λ+cK−π+π+. The data sample used corresponds to an integrated luminosity of 1.7  fb−1, collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV. The Ξ++cc lifetime is measured to be 0.256+0.024−0.022(stat)±0.014(syst)  ps

Measurement of the Ω0c Baryon Lifetime

We report a measurement of the lifetime of the Ω0c baryon using proton-proton collision data at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0  fb−1 collected by the LHCb experiment. The sample consists of about 1000  Ω−b→Ω0cμ−¯νμX signal decays, where the Ω0cbaryon is detected in the pK−K−π+ final state and X represents possible additional undetected particles in the decay. The Ω0c lifetime is measured to be τΩ0c=268±24±10±2  fs, where the uncertainties are statistical, systematic, and from the uncertainty in the D+ lifetime, respectively. This value is nearly four times larger than, and inconsistent with, the current world-average value

First Observation of the Doubly Charmed Baryon Decay Ξ++cc→Ξ+cπ+

The doubly charmed baryon decay Ξ++cc→Ξ+cπ+ is observed for the first time, with a statistical significance of 5.9σ, confirming a recent observation of the baryon in the Λ+cK−π+π+ final state. The data sample used corresponds to an integrated luminosity of 1.7  fb−1, collected by the LHCb experiment in pp collisions at a center-of-mass energy of 13 TeV. The Ξ++cc mass is measured to be 3620.6±1.5(stat)±0.4(syst)±0.3(Ξ+c)  MeV/c2 and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be[B(Ξ++cc→Ξ+cπ+)×B(Ξ+c→pK−π+)]/[B(Ξ++cc→Λ+cK−π+π+)×B(Λ+c→pK−π+)]=0.035±0.009(stat)±0.003(syst)

First Measurement of Charm Production in its Fixed-Target Configuration at the LHC

The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J/ψ and D0 mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of √sNN=86.6 and 110.4 GeV, respectively. The J/ψ and D0 production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be σJ/ψ=652±33(stat)±42(syst)   nb/nucleon and σD0=80.8±2.4(stat)±6.3(syst)  μb/nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-x region