arXiv subjects

A. De Rujula

Publications and source records attributed to A. De Rujula.

At least 19 recordsLinked to original sources

arXiv2025

The Rise of Particle Physics

Discovery of the J Particle at Brookhaven National Laboratory and the Physics of Electrons and Positrons; The Standard Model Yesterday, Today and Tomorrow; The Rise of Gauge Theories: From Many Models to One Theory; From Charm to CP Violation; When the Standard Model Was Ignored; The Discovery of the W and Z Bosons at the CERN Proton-Antiproton Collider; A Personal History of CERN Particle Colliders (1972-2022); The Age of Gravitational Wave Astronomy; Precision Physics in the Era of (HL)LHC; Recent Developments in Flavor Physics, the Unitary Triangle Fit, Anomalies and All That; About BSM Physics, with Emphasis on Flavour; The Discovery of the Antiproton between Rome and Berkeley; Raoul Gatto and Bruno Touschek: the Rise of $e+e^-$ Physics; From ADONE's Multi-Hadron Production to the J/$Ψ$ Discovery; From Bjorken Scaling to Scaling Violations

hep-ph↗

arXiv2020

Further studies on the physics potential of an experiment using LHC neutrinos

We discuss an experiment to investigate neutrino physics at the LHC in Run 3, with emphasis on tau flavour. As described in our previous paper [arXiv:1903.06564v1], the detector can be installed in the decommissioned TI18 tunnel, about 480 m downstream the ATLAS cavern, after the first bending dipoles of the LHC arc. In that location, the prolongation of the beam Line-of-Sight from Interaction Point IP1 to TI18 traverses about 100 m of rock. The detector intercepts the intense neutrino flux, generated by the LHC beams colliding in IP1, at large pseudorapidity eta, where neutrino energies can exceed a TeV. This paper focuses on optimizing global features of the experiment, like detector mass and acceptance. Since the neutrino-nucleon interaction cross section grows almost linearly with energy, the detector can be light and still collect a considerable sample of neutrino events; in the present study it weighs less than 3 tons. The detector is positioned off the beam axis, slightly above the ideal prolongation of the LHC beam from the straight section, covering 7.4 < eta < 9.2. In this configuration, the flux at high energies (0.5-1.5 TeV and beyond) is found to be dominated by neutrinos originating directly from IP1, mostly from charm decays, of which about 50% are electron neutrinos and about 5% are tau neutrinos. The contribution of pion and kaon decays to the muon neutrino flux is studied by means of simulations that embed the LHC optics and found small at high energies. The above studies indicate that with 150 /fb of delivered LHC luminosity in Run 3 the experiment can record a few thousand very high energy neutrino charged current interactions and over 50 tau neutrino charged current events.

hep-ex↗

arXiv2019

XSEN: a $ν$N Cross Section Measurement using High Energy Neutrinos from pp collisions at the LHC

XSEN (Cross Section of Energetic Neutrinos) is a small experiment designed to study, for the first time, neutrino-nucleon interactions (including the tau flavour) in the 0.5-1 TeV neutrino energy range. The detector will be installed in the decommissioned TI18 tunnel and uses nuclear emulsions. Its simplicity allows construction and installation before the LHC Run 3, 2021-2023; with 150/fb in Run3, the experiment can record up to two thousand neutrino interactions, and up to a hundred tau neutrino events. The XSEN detector intercepts the intense neutrino flux, generated by the LHC beams colliding in IP1, at large pseudo-rapidities, where neutrino energies can exceed the TeV. Since the neutrino-N interaction cross section grows almost linearly with energy, the detector can be light and still collect a considerable sample of neutrino interactions. In our proposal, the detector weighs less than 3 tons. It is lying slightly above the ideal prolongation of the LHC beam from the straight section; this configuration, off the beam axis, although very close to it, enhances the contribution of neutrinos from c and b decays, and consequently of tau neutrinos. The detector fits in the TI18 tunnel without modifications. We plan for a demonstrator experiment in 2021 with a small detector of about 0.5 tons; with 25/fb, nearly a hundred interactions of neutrinos of about 1 TeV can be recorded. The aim of this pilot run is a good in-situ characterisation of the machine-generated backgrounds, an experimental verification of the systematic uncertainties and efficiencies, and a tuning of the emulsion analysis infrastructure and efficiency. This Letter provides an overview of the experiment motivations, location, design constraints, technology choice, and operation.

physics.ins-det↗

arXiv2016

Hyperluminal Signatures in the Afterglows of Gamma-Ray Bursts 980425 and 030329

The late-time high-resolution X-ray and radio observations of GRB980425/SN1998bw, the closest known gamma ray burst (GRB) associated with a supernova (SN) explosion, may have actually resolved the hyperluminal source that produced the GRB and its afterglow. Its hyperluminal speed ~350c is consistent with that expected in the cannonball (CB) model of GRBs. The observed superluminal expansion of the late-time radio image of GRB030329/SN2003dh, the GRB with the brightest and longest followed up radio afterglow to date, is also consistent with that expected in the CB model of GRBs and extrapolates to an apparent early-time hyperluminal expansion.

astro-ph.HE↗

arXiv2013

The Future of Neutrino Mass Measurements: Terrestrial, Astrophysical, and Cosmological Measurements in the Next Decade. Highlights of the NuMass 2013 Workshop. Milano, Italy, February 4 - 7, 2013

The third Workshop of the NuMass series ("The Future of Neutrino Mass Measurements: Terrestrial, Astrophysical, and Cosmological Measurements in the Next Decade: NuMass 2013") was held at Dipartimento di Fisica "G. Occhialini, University of Milano-Bicocca in Milano, Italy, on 4-7 February 2013. The goal of this international workshop was to review the status and future of direct and indirect neutrino mass measurements in the laboratory as well as from astrophysical and cosmological observations. This paper collects most of the contributions presented during the Workshop.

hep-ex↗

arXiv2011

Origin of the Ultrahigh-Energy Cosmic Rays and their Spectral Break

The energy spectrum, composition and arrival directions of ultrahigh energy cosmic rays (UHECRs) with energy above the cosmic ray ankle, measured by the Pierre Auger Observatory, are inconsistent if their origin is assumed to be extragalactic. Their observed properties, however, are those expected from UHECRs accelerated by the highly relativistic jets emitted in Galactic gamma ray bursts, most of which are beamed away from Earth. If this alternative interpretation is correct, the observed break in the energy spectrum of UHECRs around 50 EeV is not the Greisen-Zatsepin-Kuzmin cutoff but the energy threshold for free escape of ultrahigh energy iron cosmic rays from the Galaxy and above their respective free-escape threshold-energies, UHECR nuclei should point back to their Galactic sources or their remnants rather than to active galactic nuclei (AGN) within the GZK horizon.

astro-ph.HE↗

arXiv2010

To be or not to be: Higgs impostors at the LHC

Consider the day when an invariant mass peak, roughly compatible with "the Higgs", begins to emerge, say at the LHC, ... and may you see that day. There will be a difference between discovery and scrutiny. The latter would involve an effort to ascertain what it is, or is not, that has been found. It turns out that the two concepts are linked: Scrutiny will naturally result in deeper knowledge - is this what you were all looking for? - but may also speed up discovery.

hep-ph↗

arXiv2010

Higgs look-alikes at the LHC

The discovery of a Higgs particle is possible in a variety of search channels at the LHC. However the true identity of any putative Higgs boson will at first remain ambiguous, until one has experimentally excluded other possible assignments of quantum numbers and couplings. We quantify to what degree one can discriminate a Standard Model Higgs boson from "look-alikes" at, or close to, the moment of discovery at the LHC. We focus on the fully-reconstructible "golden" decay mode to a pair of Z bosons and a four-lepton final state, simulating sPlot-weighted samples of signal and background events. Considering both on-shell and off-shell Z's, we show how to utilize the full decay information from the events, including the distributions and correlations of the five relevant angular variables. We demonstrate how the finite phase space acceptance of any LHC detector sculpts the decay distributions, a feature neglected in previous studies. We use likelihood ratios to discriminate a Standard Model Higgs from look-alikes with other spins or nonstandard parity, CP, or form factors. For a benchmark resonance mass of 200 GeV/c^2, we achieve a median expected discrimination significance of 3 sigma with as few as 19 events, and even better discrimination for the off-shell decays of a 145 GeV/c^2 resonance.

hep-ph↗

arXiv2009

The diverse broad-band light-curves of Swift GRBs reproduced with the cannonball model

Two radiation mechanisms, inverse Compton scattering (ICS) and synchrotron radiation (SR), suffice within the cannonball (CB) model of long gamma ray bursts (LGRBs) and X-ray flashes (XRFs) to provide a very simple and accurate description of their observed prompt emission and afterglows. Simple as they are, the two mechanisms and the burst environment generate the rich structure of the light curves at all frequencies and times. This is demonstrated for 33 selected Swift LGRBs and XRFs, which are well sampled from early until late time and faithfully represent the entire diversity of the broad-band light curves of Swift LGRBs and XRFs. Their prompt gamma-ray and X-ray emission is dominated by ICS of `glory' light. During their fast decline phase, ICS is taken over by SR, which dominates their broad-band afterglow. The pulse shape and spectral evolution of the gamma-ray peaks and the early-time X-ray flares, and even the delayed optical `humps' in XRFs, are correctly predicted. The `canonical' and non-canonical X-ray light curves and the chromatic behaviour of the broad-band afterglows are well reproduced. In particular, in canonical X-ray light curves, the initial fast decline and rapid softening of the prompt emission, the transition to the plateau phase, the subsequent gradual steepening of the plateau to an asymptotic power-law decay, and the transition from chromatic to achromatic behaviour of the light curves agrees well with those predicted by the CB model. The Swift early-time data on XRF 060218 are inconsistent with a black-body emission from a shock break-out through a stellar envelope. Instead, they are well described by ICS of glory light by a jet breaking out from SN2006aj.

astro-ph↗

arXiv2008

'Jet breaks' and 'missing breaks' in the X-Ray afterglow of Gamma Ray Bursts

The X-ray afterglows (AGs) of Gamma-Ray Bursts (GRBs) and X-Ray Flashes (XRFs) have, after the fast decline phase of their prompt emission, a temporal behaviour varying between two extremes. A large fraction of these AGs has a 'canonical' light curve which, after an initial shallow-decay 'plateau' phase, 'breaks smoothly' into a fast power-law decline. Very energetic GRBs, contrariwise, appear not to have a 'break', their AG declines like a power-law from the start of the observations. Breaks and 'missing breaks' are intimately related to the geometry and deceleration of the jets responsible for GRBs. In the frame of the 'cannonball' (CB) model of GRBs and XRFs, we analyze the cited extreme behaviours (canonical and pure power-law) and intermediate cases spanning the observed range of X-ray AG shapes. We show that the entire panoply of X-ray light-curve shapes --measured with Swift and other satellites-- are as anticipated, on very limpid grounds, by the CB model. We test the expected correlations between the AG's shape and the peak- and isotropic energies of the prompt radiation, strengthening a simple conclusion of the analysis of AG shapes: in energetic GRBs the break is not truly 'missing', it is hidden under the tail of the prompt emission, or it occurs too early to be recorded. We also verify that the spectral index of the unabsorbed AGs and the temporal index of their late power-law decline differ by half a unit, as predicted.

astro-ph↗

arXiv2008

Is there anything special about GRB 080319B?

We show that the properties of gamma ray burst 080319B and its afterglow are well reproduced by the cannonball model of long gamma ray bursts (GRBs). It was an ordinary GRB, produced by a jet of highly relativistic plasmoids (CBs), ejected in a core-collapse supernova (SN) and viewed, as some others before, particularly close to the CB-emission axis. It still remains to be seen whether GRB 080319B was associated with an SN akin to SN1998bw, the SN type ordinarily associated with GRBs, or with a much more luminous SN.

astro-ph↗

arXiv2008

The rapid decline of the prompt emission in Gamma-Ray Bursts

Many gamma ray bursts (GRBs) have been observed with the Burst-Alert and X-Ray telescopes of the Swift satellite. The successive `pulses' of these GRBs end with a fast decline and a fast spectral softening, until they are overtaken by another pulse, or the last pulse's decline is overtaken by a less rapidly-varying `afterglow'. The fast decline-phase has been attributed, in the currently-explored standard fireball model of GRBs, to `high-latitude' synchrotron emission from a collision of two conical shells. This high latitude emission does not explain the observed spectral softening. In contrast, the temporal behaviour and the spectral evolution during the fast-decline phase agree with the predictions of the cannonball model of GRBs.

astro-ph↗

arXiv2008

Interpreting the X-ray Flash XRF 060218 and its associated supernova

Forty years after their discovery, and in spite of a very large body of observations, the operation of the 'engine' responsible for long-duration Gamma-Ray Bursts (GRBs) and X-ray flashes --as well as the mechanisms generating their radiation-- are still the subject of debate and study. In this respect a recent event, XRF 060218, associated with SN 2006aj, is particularly significant. It has been argued that, for the first time, the break-out of the shock involved in the supernova explosion has been observed, thanks to the detection of a thermal component in the event's radiation; that this XRF was not a GRB seen 'off-axis', but a member of a new class of energetically feeble GRBs; and that its 'continued engine activity' may have been driven by a remnant highly-magnetized neutron star, a magnetar. I argue, on grounds based on observations and on limpid verified hypothesis, that there is a common, simpler alternative to these views, with no thermal component, no new feeble GRBs, and no steady engine activity.

astro-ph↗

arXiv2007

Long gamma-ray bursts without visible supernovae: a case study of redshift estimators and alleged novel objects

It has been argued that the observational limits on a supernova (SN) associated with GRB060614 convincingly exclude a SN akin to SN1998bw as its originator, and provide evidence for a new class of long-duration GRBs. We discuss this issue in the contexts of indirect 'redshift estimators' and of the fireball and cannonball models of GRBs. The latter explains the unusual properties of GRB060614: at its debated but favoured low redshift (0.125) they are predicted, as opposed to exceptional, if the associated core-collapse SN is of a recently discovered, very faint type. We take the occasion to discuss the 'association' between GRBs and SNe.

astro-ph↗

arXiv2007

An introduction to Cosmic Rays and Gamma-Ray Bursts, and to their simple understanding

I review the subjects of non-solar cosmic rays (CRs) and long-duration gamma-ray bursts (GRBs). Of the various interpretations of these phenomena, the one best supported by the data is the following. Accreting compact objects, such as black holes, are seen to emit relativistic puffs of plasma: `cannonballs' (CBs). The inner domain of a rotating star whose core has collapsed resembles such an accreting system. This suggests that core-collapse supernovae (SNe) emit CBs, as SN1987A did. The fate of a CB as it exits a SN and travels in space can be studied as a function of the CB's mass and energy, and of `ambient' properties: the encountered matter- and light- distributions, the composition of the former, and the location of intelligent observers. The latter may conclude that the interactions of CBs with ambient matter and light generate CRs and GRBs, all of whose properties can be described by this `CB model' with few parameters and simple physics. GRB data are still being taken in unscrutinized domains of energy and timing. They agree accurately with the model's predictions. CR data are centenary. Their precision will improve, but new striking predictions are unlikely. Yet, a one-free-parameter description of all CR data works very well. This is a bit as if one discovered QED today and only needed to fit $α$.

hep-ph↗

arXiv2007

Gamma ray bursts, supernovae and metallicity in the intergalactic medium

The mean iron abundance observed in the intergalactic medium (IGM) within galaxy clusters and without galaxy clusters is consistent with the mean amount of iron per unit volume in the Universe which has been produced by standard supernova (SN) explosions with a rate proportional to the cosmic star-formation rate. If most SNe took place inside galaxies, then the IGM could have been enriched with their metals by galactic winds and jets that swept most of the galactic gas with the SNe ejecta into the IGM. A significant fraction of the early SNe, however, could have taken place outside galaxies or within dwarf galaxies, which were later disrupted by tidal interactions, and/or mass loss through fast winds, SN ejecta and jets. Little is known about such intergalactic SNe at high red-shifts. They could have occurred primarily in highly obscured environments, avoiding detection. Supporting evidence for intergalactic SNe is provided by SNe associated with gamma ray bursts (GRBs) without a host galaxy and from the ratio of well localized GRBs with and without a host galaxy. A direct test of whether a significant contribution to the iron abundance in the IGM came from intergalactic SNe would require the measurement of their rate per comoving unit volume as function of red-shift. This may be feasible with IR telescopes, such as the Spitzer Space Telescope.

astro-ph↗

arXiv2007

What SWIFT has taught us about X-ray flashes and long-duration gamma-ray bursts

Recent data gathered and triggered by the SWIFT satellite have greatly improved our knowledge of long-duration gamma ray bursts (GRBs) and X-ray flashes (XRFs). This is particularly the case for the X-ray data at all times, and for UV and optical data at very early times. I show that the optical and X-ray observations are in excellent agreement with the predictions of the "cannonball" model of GRBs and XRFs. Elementary physics and just two mechanisms underlie these predictions: inverse Compton scattering and synchrotron radiation, generally dominant at early and late times, respectively. I put this result in its proper context and dedicate the paper to those who planed, built and operate SWIFT, a true flying jewel.

astro-ph↗

arXiv2007

The time ending the shallow decay of the X-ray light curves of long GRBs

We show that the mean values and distributions of the time ending the shallow decay of the light curve of the X-ray afterglow of long gamma ray bursts (GRBs), the equivalent isotropic energy in the X-ray afterglow up to that time and the equivalent isotropic GRB energy, as well as the correlations between them, are precisely those predicted by the cannonball (CB) model of GRBs. Correlations between prompt and afterglow observables are important in that they test the overall consistency of a GRB model. In the CB model, the prompt and afterglow spectra, the endtime, the complex canonical shape of the X-ray afterglows and the correlations between GRB observables are not surprises, but predictions.

astro-ph↗