The Universal One-Loop Effective Action

We present the universal one-loop effective action for all operators of dimension up to six obtained by integrating out massive, non-degenerate multiplets. Our general expression may be applied to loops of heavy fermions or bosons, and has been checked against partial results available in the literature. The broad applicability of this approach simplifies one-loop matching from an ultraviolet model to a lower-energy effective field theory (EFT), a procedure which is now reduced to the evaluation of a combination of matrices in our universal expression, without any loop integrals to evaluate. We illustrate the relationship of our results to the Standard Model (SM) EFT, using as an example the supersymmetric stop and sbottom squark Lagrangian and extracting from our universal expression the Wilson coefficients of dimension-six operators composed of SM fields.Comment: 30 pages, v2 contains additional comments and corrects typos, version accepted for publication in JHE

Patterns in the development of collective immunity to SARS-CoV-2 during the COVID-19 pandemic

The ongoing coronavirus disease (COVID-19) pandemic over the past three years has caused close attention to the problem of herd immunity, which is understood as: "resistance to the spread of a contagious disease within a population or herd". Collective immunity is formed both as a result of infection (natural spread of the pathogen in a population of susceptible individuals) and as a result of the use of specific vaccines. During the COVID-19 pandemic, both mechanisms for the formation of collective immunity were realized. In the first wave, there was a natural formation of collective immunity to the virus following recoveries from COVID-19 caused by pandemic spread of SARS-CoV-2. Starting from December 2020, the widespread use of specific vaccines against SARS-CoV-2 began in the USA, Great Britain, China, Russia, and a number of other countries. This launched the process of post-vaccination collective immunity formation; its features have depended on the vaccine types implemented. Currently, in those countries where vaccination and revaccination of recovered patients is widely carried out, immunity is "hybrid" in nature. Several commonalities should be noted in the pandemic experience: a somewhat regular, periodic (wavelike) nature of the COVID-19 epidemic process; changes in pathogen genetics in variants in all countries; and expansive mass vaccination programs in many populations. From these, we can draw some conclusions about the general trend for all countries in the formation of collective immunity during the pandemic: At the beginning of the pandemic in 2020, overall population seroprevalence did not exceed 20%. Other findings were: the highest seroprevalence rates were noted in the children's age group; pronounced regional differences were revealed; and the highest indicators were noted among medical workers. Collective immunity developed as a result of infection or illness, and in the majority of seropositive volunteers, it was represented by antibodies to both antigens. At the height of the pandemic in the summer of 2021, population seroprevalence reached 50%. This was due to both a significant number of convalescents and the start of mass vaccination campaigns. In all countries, specific differences in seroprevalence (by age, region, profession) leveled out, leading to more uniformity. During this period, the formation of "hybrid" immunity is clearly prominent, and the proportion of individuals with antibodies to RBD alone increased (due to vaccination with vector vaccines).  Later, mass vaccination, as well as involvement of most of the population in the epidemic process due to the emergence of the highly contagious Omicron strain, raised the level of collective immunity to 80-90%. This led to a sharp decrease in COVID-19 incidence in the second half of 2022 in all countries participating in the study. In the later stages of the pandemic (2022-2023), almost 90% of seropositive volunteers had hybrid immunity, reflected as antibodies to both antigens (Nc, RBD)

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal

Isospin violating dark matter in Stückelberg portal scenarios

Journal of High Energy Physics 2015.4 (2015): 175 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)Hidden sector scenarios in which dark matter (DM) interacts with the Standard Model matter fields through the exchange of massive Z′ bosons are well motivated by certain string theory constructions. In this work, we thoroughly study the phenomenological aspects of such scenarios and find that they present a clear and testable consequence for direct DM searches. We show that such string motivated Stückelberg portals naturally lead to isospin violating interactions of DM particles with nuclei. We find that the relations between the DM coupling to neutrons and protons for both, spin-independent (fn/fp) and spin-dependent (an/ap) interactions, are very flexible depending on the charges of the quarks under the extra U(1) gauge groups. We show that within this construction these ratios are generically different from ±1 (i.e. different couplings to protons and neutrons) leading to a potentially measurable distinction from other popular portals. Finally, we incorporate bounds from searches for dijet and dilepton resonances at the LHC as well as LUX bounds on the elastic scattering of DM off nucleons to determine the experimentally allowed values of fn/fp and an/apThe authors are grateful to D. G. Cerdeño, L. Ibañez, F. Kahlhoefer and G. Shiu for useful comments. V.M.L. and M.P. would like to thank the support of the European Union under the ERC Advanced Grant SPLE under contract ERC-2012-ADG-20120216-320421, the support of the Consolider-Ingenio 2010 programme under grant MULTIDARK CSD2009-00064, the Spanish MICINN under Grant No. FPA2012-34694, the Spanish MINECO “Centro de excelencia Severo Ochoa Program” under Grant No. SEV-2012-0249, and the Community of Madrid under Grant No. HEPHACOS S2009/ESP-1473. P.S. would like to thank DESY, the University of Hamburg, and the Hong Kong IAS for kind hospitality during the completion of this work. He acknowledges support from the DOE grant DEFG-02-95ER40896 and the HKRGC grant HKUST4/CRF/13G, 604231, as well as the Collaborative Research Center SFB676 of the DFG at the University of Hambur

Monitoring of coronavirus infection in the kyrgyz population

Purpose of the study: to study the dynamics of developing herd immunity against SARS-CoV-2 in the population of the Republic of Kyrgyzstan during COVID-19. Materials and methods. The work was carried out using the methodology for assessing population immunity developed by Rospotrebnadzor (Russia) as well as the Ministry of Health (Kypgyzstan) and the St. Petersburg Pasteur Institute. The selection of participants was carried out by questionnaire using a cloud (Internet server) service. To monitor population immunity, a cohort of 2421 subjects was formed, who participated in all stages of seromonitoring. Volunteers were randomized according to age groups (1–17, 18–29, 30–39, 40–49, 50–59, 60–69, 70+ years), regional and professional factors. Antibodies (Abs) against SARS-CoV-2 nucleocapsid (Nc) and the receptor binding domain (RBD) of S-glycoprotein were determined by qualitative and quantitative methods. The study was carried out in 3 stages according to a single scheme: 1st stage — 06/28–07/03/2021, 2nd — 21–25/02/2022 and 3rd — 31/10–04/11/2022. Since 2021, Kyrgyzstan has been vaccinating the population against SARS-CoV-2 mainly using inactivated whole-virion vaccines. Results. Population immunity against SARS-CoV-2 was predominantly accounted for by both Ab types (Nc+RBD+). By the 3rd stage, the percentage of such persons reached 99.2%, Nc–RBD– volunteers — up to 0.8%. At the 1st stage, middle-aged people dominated, but age differences were leveled out by the 2nd stage. The greatest impact on seroprevalence was found among medical workers, the smallest — among businessmen and industrial workers. Populational vaccination significantly impacted on the state of herd immunity that reached 25% by the 3rd stage. The refusals of the population in Kyrgyz Republic from vaccination noted at the 2nd and especially 3rd stages did not significantly affect level of herd immunity, which could probably be associated with asymptomatic cases of COVID-19, against which primary vaccination had a booster effect. Conclusion. The dynamics of population humoral immunity against SARS-CoV-2 included a number of changes in the level of circulating antibodies (Nc, RBD), caused by both primary infection and vaccination. The herd immunity formed in population of Kyrgyzstan allowed to reduce the incidence of COVID-19 to almost sporadic level

Dimension-6 operator analysis of the CLIC sensitivity to new physics

We estimate the possible accuracies of measurements at the proposed CLICe+ e− collider of Higgs and W+W− production at centre-of-mass energies up to 3 TeV, incorporating also Higgsstrahlung projections at higher energies that had not been considered previously, and use them to explore the prospective CLIC sensitivities to decoupled new physics. We present the resulting constraints on the Wilson coefficients of dimension6 operators in a model-independent approach based on the Standard Model effective field theory (SM EFT). The higher centre-of-mass energy of CLIC, compared to other projects such as the ILC and CEPC, gives it greater sensitivity to the coefficients of some of the operators we study. We find that CLIC Higgs measurements may be sensitive to new physics scales Λ = O(10) TeV for individual operators, reduced to O(1) TeV sensitivity for a global fit marginalising over the coefficients of all contributing operators. We give some examples of the corresponding prospective constraints on specific scenarios for physics beyond the SM, including stop quarks and the dilaton/radion

WASA-FRS experiments in FAIR Phase-0 at GSI

We have developed a new and unique experimental setup integrating the central part of the Wide Angle Shower Apparatus (WASA) into the Fragment Separator (FRS) at GSI. This combination opens up possibilities of new experiments with high-resolution spectroscopy at forward and measurements of light decay particles with nearly full solid-angle acceptance in coincidence. The first series of the WASA-FRS experiments have been successfully carried out in 2022. The developed experimental setup and two physics experiments performed in 2022 including the status of the preliminary data analysis are introduced

Effective description of general extensions of the Standard Model: the complete tree-level dictionary

We thank Nuria Rius and Arcadi Santamaria for an interesting discussion that motivated this work. We also thank Paco del Águila and Toni Pich for useful comments.We compute all the tree-level contributions to the Wilson coefficients of the dimension-six Standard-Model effective theory in ultraviolet completions with general scalar, spinor and vector feld content and arbitrary interactions. No assumption about the renormalizability of the high-energy theory is made. This provides a complete ultraviolet/ infrared dictionary at the classical level, which can be used to study the low-energy implications of any model of interest, and also to look for explicit completions consistent with low-energy dataThe work of J.C.C., M.P.V. and J.S. has been supported by the Spanish MICINN project FPA2013- 47836-C3-2-P, the MINECO project FPA2016-78220-C3-1-P (Fondos FEDER) and the Junta de Andalucía grant FQM101. The work of J.C.C. has also been supported by the Spanish MECD grant FPU14. The work of M.P.V. and J.S. has also been supported by the European Commission through the contract PITN-GA-2012-316704 (HIGGSTOOLS). J.C.C. is grateful for the hospitality of the Dipartimento di Fisica e Astronomia \Galileo Galilei" of the University of Padova during part of this work. J.S. would like to thank the Mainz Institute for Theoretical Physics (MITP) for its hospitality and partial support during the completion of this work