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A. De Rújula

Publications and source records attributed to A. De Rújula.

At least 19 recordsLinked to original sources
arXiv2026

Measurement of the muon neutrino charged-current cross section with SND@LHC

We report a measurement of the muon neutrino charged-current (CC) interaction cross section on tungsten using the electronic detectors of the SND@LHC experiment at the CERN Large Hadron Collider. The analysis uses proton--proton collision data at a centre-of-mass energy of $\sqrt{s} = 13.6$ TeV, corresponding to an integrated luminosity of $68.6 ~\text{fb}^{-1}$ collected during LHC Run 3 in 2022 and 2023. A total of 31 $ν_μ$ CC candidates are selected against an expected background of $5.0 \pm 1.1$ events, consistent with a signal expectation of $24^{+10}_{-9}$ events. The signal strength is measured to be $\hatμ = 1.09^{+0.72}_{-0.37}$, and the combined muon neutrino and anti-neutrino CC cross section on tungsten is determined to be $σ(ν_μ+ \barν_μ) = (37^{+24}_{-12})\times 10^{-35}~\text{cm}^2$ at a median energy of $228$ GeV. In addition, a calorimetric measurement of the hadronic energies of the neutrino candidate events is performed, making use of calibration data from dedicated test-beam campaigns.

hep-ex↗
arXiv2026

Human versus Artificial Intelligence; various significant examples in astrophysics

In a recent arXiv posting [1] I reported the result of an experiment: asking Perplexity.ai to compare three items concerning (ordinary) Gamma Ray Burts (GRBs): the data, the standard paradigm(s) and the "Cannonball" (CB) model. Here I ask the same URL to extend this comparison to long--lasting GRBs, binary Neutron-Star mergers and their associated short--hard GRBs, low--luminosity GRBs, X--ray flashes, X--ray transients, and non--solar cosmic rays. The results of this experiment are enlightening but worrisome. Except for this abstract, two footnotes and two other references to standard [2] and CB-model [3] articles and talks, all of what follows is, verbatim, what the cited AI "opines".

astro-ph.HE↗
arXiv2026

Human versus Artificial Inteligence; a significant example in astrophysics, alas

There are two well documented models of gamma ray bursts (GRBs), the "Standard' model and the "Cannonball" model. They have often been reviewed [1] and sometimes compared [2]. Here, to avoid understandable biases, I show below the results of an experiment: letting an AI compare the data and the two models. All of what follows (but two references, two footnotes and the next sentence) is the result of asking Perplexity.ai to perform this confrontational task. It should be easy for an impartial reader to reach very clear conclusions.

astro-ph.HE↗
arXiv2025

High-energy photons from Gamma-Ray Bursts, but no neutrinos

The Cannon-Ball model of Gamma-Ray Bursts and their afterglows--described in the text and in innumerable previous occasions--is extremely successful and predictive. In a few intrinsically bright GRBs, gamma-rays with energies in the TeV range have been observed. The CB model, I argue, has no difficulty in describing the origin and approximate properties of these high-energy gamma rays and the extreme difficulty of observing their accompanying neutrinos.

hep-ph↗
arXiv2025

A revamped understanding of Cosmic Rays and Gamma-Ray Bursts

Interesting data on Gamma Ray Burts (GRBs) and Cosmic Rays (CRs) have recently been made public. GRB221009A has a record ``peak energy". The CR electron spectrum has been measured to unprecedented high energies and exhibits a ``knee" akin to the ones in all-particle or individual-element CR nuclei. IceCube has not seen high-energy neutrinos associated with GRBs. AMS has published a CR positron spectrum conducive to much speculation. We examine these data in the light of the ``CannonBall Model" of GRBs and CRs, in which they are intimately related and which they do strongly validate.

hep-ph↗
arXiv2022

The gravitational wave and short gamma-ray burst GW170817/SHB170817A, not your everyday binary neutron star merger

This event, so far unique, beautifully confirmed the standard views on the gravitational waves produced by a merger of two neutron stars, but its electromagnetic multi-wavelenth observations disagreed with the numerous initial versions of the "standard fireball model(s)" of gamma ray bursts. Contrariwise, they provided strong evidence in favour of the "cannonball" model. Most uncontroversially, a cannonball was observed at radio wavelengths, with an overwhelming statistical significance ($>\! 17\,σ$), and travelling in the plane of the sky, as expected, at an apparent superluminal velocity $V_{app}\sim 4\, c$.

astro-ph.HE↗
arXiv2022

Critical Tests of Leading Gamma Ray Burst Theories II

It has been observationally established that supernovae (SNe) of Type Ic produce long duration gamma ray bursts (GRBs) and that neutron star mergers generate short hard GRBs. SN-Less GRBs presumably originate in a phase transition of a neutron star in a high mass X-ray binary. How these phenomena actually generate GRBs is debated. The fireball and cannonball models of GRBs and their afterglows have been widely confronted with the huge observational data, with their defenders claiming success. The claims, however, may reflect multiple choices and the use of many adjustable parameters, rather than the validity of the models. Only a confrontation of key falsifiable predictions of the models with solid observational data can test their validity. Such critical tests are reviewed in this report.

astro-ph.HE↗
arXiv2020

Apollo 11 and Fundamental Science

Half a century after a man first set foot on the moon it is interesting to revisit the occasion with a measure of hindsight. From the point of view of basic science the greatest achievement concerned the implementation of the Nordtvedt test, a precise check of Einstein's strong equivalence principle. A particle physicist may bravely interpret the result as a precise measurement of the triple-graviton coupling. Other not so profound experiments were also (unofficially) made in Apollo flights, such as a long-distance test of ESP (yes! extra sensory perception). From a sociopolitical point of view the lesson concerns the feats that can be achieved by a determined and united country... or more than one.

physics.hist-ph↗
arXiv2019

QCD, from its inception to its stubbornly unsolved problems

Whenever one has witnessed some event and then sees it reported in the media, one's reaction is the same: "it was not quite like that". It is in this spirit of a frequent first-hand witness that I write this article. I discuss a few selected points which --to my judgement-- illustrate well the QCD evolution (in time) from the theoretical, phenomenological and experimental points of view.

hep-ph↗
arXiv2019

Deciphering the AMS cosmic-ray positron flux

The flux of cosmic-ray high-energy positrons has recently been measured by AMS with unprecedented precision. This flux is well above the expectation from secondary positrons made by the observed fluxes of nuclear cosmic rays impinging on the interstellar medium. Various authors have pointed out that the positron excess may originate at the primary cosmic-ray source itself, rather than in the more local ISM, thus avoiding the temptation to invoke a dark-matter decay or annihilation origin, or nearby pulsars. We investigate the possibility that the source is the one of a comprehensive model of gamma-ray bursts and cosmic rays, proposed two decades ago. The result, based on the original unmodified priors of the model --and with no fitting of parameters-- very closely reproduces the shape and magnitude of the AMS observations.

hep-ph↗
arXiv2019

The Cosmic-Ray Spectra: News on their Knees

In a comprehensive model of Cosmic Rays (CRs) proposed a decade ago, the energies of the spectral "knees" of the various CR species were predicted to be proportional to mass, rather than charge. The model also predicts the knees to occur at an energy of two to four million times the particle's rest mass. Recent data allow one to verify this prediction, particularly for Fe and lighter-nuclei CRs. But the most stringent test involves the putative knee in the CR electron spectrum, since the mass ratio of electrons to protons (and nuclei) is so very different from their charge ratio(s). Very recent results on the spectra of positrons and electrons at the highest measured energies corroborate the existence of an electron knee, with the expected shape and at the predicted energy.

hep-ph↗
arXiv2016

Archeology and evolution of QCD

These are excerpts from the closing talk at the "XIIth Conference on Quark Confinement and the Hadron Spectrum", which took place last Summer in Thessaloniki --an excellent place to enjoy an interest in archeology. A more complete personal view of the early days of QCD and the rest of the Standard Model is given in [1]. Here I discuss a few of the points which --to my judgement-- illustrate well the QCD evolution (in time), both from a scientific and a sociological point of view.

hep-ph↗
arXiv2016

The calorimetric spectrum of the electron-capture decay of $^{163}$Ho. The spectral endpoint region

The electron-neutrino mass (or masses and mixing angles) may be directly measurable in weak electron-capture decays. The favoured experimental technique is "calorimetric". The optimal nuclide is $^{163}$Ho, and several experiments (ECHo, HOLMES and NuMECS) are currently studying its decay. The most relevant range of the calorimetric-energy spectrum extends for the last few hundred eV below its endpoint. It has not yet been well measured. We explore the theory, mainly in the cited range, of electron capture in $^{163}$Ho decay. A so far neglected process turns out to be most relevant: electron-capture accompanied by the shake-off of a second electron. Our two main conclusions are very encouraging: the counting rate close to the endpoint may be more than an order of magnitude larger than previously expected; the "pile-up" problem may be significantly reduced.

hep-ph↗
arXiv2015

The calorimetric spectrum of the electron-capture decay of $^{163}$Ho. A preliminary analysis of the preliminary data

It is in principle possible to measure directly the electron neutrino mass (or masses and mixing angles) in weak electron-capture decays. The optimal nuclide in this respect is $^{163}$Ho. The favoured experimental technique, currently pursued in various experiments (ECHo, HOLMES and NuMECS) is "calorimetric". The calorimetric energy spectrum is a sum over the unstable vacant orbitals, or "holes", left by the electrons weakly captured by the nucleus. We discuss the current progress in this field and analize the preliminary data. Our conclusion is that, as pointed out by Robertson, the contribution of two-hole states is not negligible. But --in strong contradistinction with the tacit conclusion of previous comparisons of theory and observations-- we find a quite satisfactory agreement. A crucial point is that, in the creation of secondary holes, electron shakeoff and not only electron shakeup must be taken into account.

hep-ph↗
arXiv2013

Two old ways to measure the electron-neutrino mass

Three decades ago, the measurement of the electron neutrino mass in atomic electron capture (EC) experiments was scrutinized in its two variants: single EC and neutrino-less double EC. For certain isotopes an atomic resonance enormously enhances the expected decay rates. The favoured technique, based on calorimeters as opposed to spectrometers, has the advantage of greatly simplifying the theoretical analysis of the data. After an initial surge of measurements, the EC approach did not seem to be competitive. But very recently, there has been great progress on micro-calorimeters and the measurement of atomic mass differences. Meanwhile, the beta-decay neutrino-mass limits have improved by a factor of 15, and the difficulty of the experiments by the cube of that figure. Can the "calorimetric" EC theory cope with this increased challenge? I answer this question affirmatively. In so doing I briefly review the subject and extensively address some persistent misunderstandings of the underlying quantum physics.

hep-ph↗
arXiv2012

Singular ways to search for the Higgs boson

The discovery or exclusion of the fundamental standard scalar is a hot topic, given the data of LEP, the Tevatron and the LHC, as well as the advanced status of the pertinent theoretical calculations. With the current statistics at the hadron colliders, the workhorse decay channel, at all relevant H masses, is H to WW, followed by W to light leptons. Using phase-space singularity techniques, we construct and study a plethora of "singularity variables" meant to facilitate the difficult tasks of separating signal and backgrounds and of measuring the mass of a putative signal. The simplest singularity variables are not invariant under boosts along the collider's axes and the simulation of their distributions requires a good understanding of parton distribution functions, perhaps not a serious shortcoming during the boson hunting season. The derivation of longitudinally boost-invariant variables, which are functions of the four charged-lepton observables that share this invariance, is quite elaborate. But their use is simple and they are, in a kinematical sense, optimal.

hep-ph↗
arXiv2011

Measuring the W-Boson mass at a hadron collider: a study of phase-space singularity methods

The traditional method to measure the W-Boson mass at a hadron collider (more precisely, its ratio to the Z-mass) utilizes the distributions of three variables in events where the W decays into an electron or a muon: the charged-lepton transverse momentum, the missing transverse energy and the transverse mass of the lepton pair. We study the putative advantages of the additional measurement of a fourth variable: an improved phase-space singularity mass. This variable is statistically optimal, and simultaneously exploits the longitudinal- and transverse-momentum distributions of the charged lepton. Though the process we discuss is one of the simplest realistic ones involving just one unobservable particle, it is fairly non-trivial and constitutes a good "training" example for the scrutiny of phenomena involving invisible objects. Our graphical analysis of the phase space is akin to that of a Dalitz plot, extended to such processes.

hep-ph↗