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| 2. |
- Abbasi, Rasha, et al.
(författare)
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IceCube search for neutrinos from GRB 221009A
- 2023
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Ingår i: Proceedings of 38th International Cosmic Ray Conference (ICRC 2023). - : Sissa Medialab Srl.
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Konferensbidrag (refereegranskat)abstract
- GRB 221009A is the brightest Gamma Ray Burst (GRB) ever observed. The observed extremelyhigh flux of high and very-high-energy photons provide a unique opportunity to probe the predictedneutrino counterpart to the electromagnetic emission. We have used a variety of methods to searchfor neutrinos in coincidence with the GRB over several time windows during the precursor, promptand afterglow phases of the GRB. MeV scale neutrinos are studied using photo-multiplier ratescalers which are normally used to search for galactic core-collapse supernovae neutrinos. GeVneutrinos are searched starting with DeepCore triggers. These events don’t have directionallocalization, but instead can indicate an excess in the rate of events. 10 GeV - 1 TeV and >TeVneutrinos are searched using traditional neutrino point source methods which take into accountthe direction and time of events with DeepCore and the entire IceCube detector respectively. The>TeV results include both a fast-response analysis conducted by IceCube in real-time with timewindows of T0 − 1 to T0 + 2 hours and T0 ± 1 day around the time of GRB 221009A, as well asan offline analysis with 3 new time windows up to a time window of T0 − 1 to T0 + 14 days, thelongest time period we consider. The combination of observations by IceCube covers 9 ordersof magnitude in neutrino energy, from MeV to PeV, placing upper limits across the range forpredicted neutrino emission.
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| 3. |
- Bijnens, Johan, et al.
(författare)
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Leading Logarithms in the Massive $O(N)$ Nonlinear Sigma Model
- 2010
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 827:1-2, s. 237-255
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Tidskriftsartikel (refereegranskat)abstract
- We review Buchler and Colangelo's result that leading divergences at any loop order can be calculated using only one-loop calculations and we provide an alternative proof. We then use this method to calculate the leading divergences of and thus the leading logarithmic corrections to the meson mass in the massive $O(N)$ nonlinear sigma model to five-loop order. We also calculate the all-loop result to leading order in the large $N$ expansion by showing that only cactus diagrams contribute and by summing these via a generalized gap equation.
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| 4. |
- Bijnens, Johan, et al.
(författare)
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The massive O(N) non-linear sigma model at high orders
- 2011
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 843:1, s. 55-83
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Tidskriftsartikel (refereegranskat)abstract
- We extend our earlier work on the massive O(N) non-linear sigma model to other observables. We derive expressions at leading order in the large N expansion at all orders in the loop expansion for the decay constant, vacuum expectation value, meson meson scattering and the scalar and vector form factors. This is done using cactus diagram resummation using a generalized gap equation and other recursion relations. For general N we derive the expressions for the n-th-loop-order leading logarithms (M-2/F-2 log(mu(2)/M-2))(n), up to five loops for the decay constant and vacuum expectation value (VEV) and up to four loops for meson-meson scattering, the scalar and vector form factors. We also quote our earlier result for the mass. The large N results do not give a good approximation for the case N = 3. We use our results to study the convergence of the perturbative series and compare with elastic unitarity. (C) 2010 Elsevier B.V. All rights reserved.
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| 5. |
- Carloni, Lisa, et al.
(författare)
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Discerning secluded sector gauge structures
- 2011
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Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479. ; :4
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Tidskriftsartikel (refereegranskat)abstract
- New fundamental particles, charged under new gauge groups and only weakly coupled to the standard sector, could exist at fairly low energy scales. In this article we study a selection of such models, where the secluded group either contains a softly broken U(1) or an unbroken SU(N). In the Abelian case new gamma(v) gauge bosons can be radiated off and decay back into visible particles. In the non-Abelian case there will not only be a cascade in the hidden sector, but also hadronization into new pi(v) and rho(v) mesons that can decay back. This framework is developed to be applicable both for e(+) e(-) and pp collisions, but for these first studies we concentrate on the former process type. For each Abelian and non-Abelian group we study three different scenarios for the communication between the standard sector and the secluded one. We illustrate how to distinguish the various characteristics of the models and especially study to what extent the underlying gauge structure can be determined experimentally.
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| 6. |
- Carloni, Lisa
(författare)
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Renormalization in Effective Field Theory and Hidden Radiation
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis dealswith the field of high-energy particle physics. It ismainly concernedwith two issues: the “renormalization of effective field theories” and the “detection of hidden sectors”. The first two papers are dedicated to the renormalization issue while the second two deal with the hidden sectors. Renormalization is crucial when one calculates physical observables to a high degree of precision in quantum field theory using perturbative expansions. The field has lately seen many new developments, a recent one is the Weinberg-B¨uchler-Colangelo algorithm for calculating so-called Leading Logarithms (LL). These terms appear at each refinement of the calculation of a physical observable, i.e. at higher-orders in the perturbative expansion. They can be used to give a rough estimate of the size of each higher-order correction (refinement), to verify that each new calculation will yield a small correction to the previous estimate. This way, once the desired precision is reached, one can be sure that ulterior (often lengthy) calculations will not be necessary. In paper I we apply the algorithmto the calculation of the mass, in a particularly simple model called O(N + 1)/O(N) non-linear massive sigma model. Though the model has a simple structure, it has the interesting feature that for N = 3 it describes two-flavour ChPT (chiral perturbation theory), the theory for lowenergy particle interactions, like π −π scattering. In paper II we apply the algorithmto the decay constant, the vacuumexpectation value, the scattering amplitude, the pion scalar and vector form factors. We perform the calculation to very high precision (the first four or five LLs, depending on the observable), and showin which cases it is preferable to express the logs in terms of the physical observables and in which cases in terms of the model parameters. We also solve (part of) the longstanding problem of summing the contributions of infinite refinements, for all these observables.We do this in the large number of fields N limit approximation.We prove this to be a poor approximation of the generic N expressions for most observables. The second topic deals with the detection of new hypothetical light mass particle sectors, hidden from ordinary matter by an energy barrier. We exploit the high energies reached by particle colliders to breach the barrier and observe the deviations from standard particle distributions induced by the hidden sector. We consider both hadron colliders like LHC in CERN, where protons collide, and the case of lepton colliders, where electron and positron collide. We develop models and tools to simulate the effects of these new particles. The tools are inserted in a full scale random Monte Carlo event generator called PYTHIA 8. This is used to simulate particle collisions, so that one can connect the probabilities calculated from the theory with the particle distributions observed in the detectors. In paper III we explore the idea of discovering a new hidden sector charge through the effects of its radiation on the standard particle kinematics. In paper IV we seek to determine the structure of said charges, through differences between the induced radiation and hadronization patterns and the subsequent effects on standard distributions.
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| 7. |
- Carloni, Lisa, et al.
(författare)
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Visible effects of invisible Hidden Valley radiation
- 2010
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :9, s. 1-31
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Tidskriftsartikel (refereegranskat)abstract
- Assuming there is a new gauge group in a Hidden Valley, and a new type of radiation, can we observe it through its effect on the kinematic distributions of recoiling visible particles? Specifically, what are the collider signatures of radiation in a hidden sector? We address these questions using a generic SU(N)-like Hidden Valley model that we implement in PYTHIA. We find that in both the e(+)e(-) and the LHC cases the kinematic distributions of the visible particles can be significantly affected by the valley radiation. Without a proper understanding of such effects, inferred masses of "communicators" and of invisible particles can be substantially off.
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