PBSP Collaboration, Costantini MN, Hammou E, Kassabov Z, Madigan M, Mantani L, Morales-Alvarado M, Moore JM, Ubiali M. SIMUnet: an open-source tool for simultaneous global fits of EFT Wilson coefficients and PDFs

We present the open-source SIMUnet code, designed to fit Standard Model Effective Field Theory (SMEFT) Wilson coefficient alongside Parton Distribution Functions (PDFs) of the proton. SIMUnet can perform SMEFT global fits, as well as simultaneous fits of the PDFs and of an arbitrarily large number of SMEFT degrees of freedom, by including both PDF-dependent and PDF-independent observables. SIMUnet can also be used to determine whether the effects of any New Physics models can be fitted away in a global fit of PDFs. SIMUnet is built upon the open-source NNPDF code and is released together with documentation, and tutorials. To illustrate the functionalities of the new tool, we present a new global analysis of the SMEFT Wilson coefficients accounting for their interplay with the PDFs. We increment our previous analysis of the LHC Run II top quark data with both (i) the Higgs production and decay rates data from the LHC, and (ii) the precision electroweak and diboson measurements from LEP and the LHC.

Combination of Searches for Resonant Higgs Boson Pair Production Using pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector

A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to 139  fb^{-1} of pp collision data at sqrt[s]=13  TeV recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: bb[over ¯]bb[over ¯], bb[over ¯]τ^{+}τ^{-}, and bb[over ¯]γγ. No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating from the decay of a narrow scalar resonance with mass in the range 251 GeV-5 TeV. The observed (expected) limits are in the range 0.96-600 fb (1.2-390 fb). The limits are interpreted in the type-I two-Higgs-doublet model and the minimal supersymmetric standard model, and constrain parameter space not previously excluded by other searches.

Search for Exotic Higgs Boson Decays H→AA→4γ with Events Containing Two Merged Diphotons in Proton-Proton Collisions at sqrt[s]=13 TeV

We present the first direct search for exotic Higgs boson decays H→AA, A→γγ in events with two photonlike objects. The hypothetical particle A is a low-mass spin-0 particle decaying promptly to a merged diphoton reconstructed as a single photonlike object. We analyze the data collected by the CMS experiment at sqrt[s]=13  TeV corresponding to an integrated luminosity of 136  fb^{-1}. No excess above the estimated background is found. We set upper limits on the branching fraction B(H→AA→4γ) of (0.9-3.3)×10^{-3} at 95% confidence level for masses of A in the range 0.1-1.2 GeV.

Search for Nonresonant Pair Production of Highly Energetic Higgs Bosons Decaying to Bottom Quarks

A search for nonresonant Higgs boson (H) pair production via gluon and vector boson (V) fusion is performed in the four-bottom-quark final state, using proton-proton collision data at 13 TeV corresponding to 138  fb^{-1} collected by the CMS experiment at the LHC. The analysis targets Lorentz-boosted H pairs identified using a graph neural network. It constrains the strengths relative to the standard model of the H self-coupling and the quartic VVHH couplings, κ_{2V}, excluding κ_{2V}=0 for the first time, with a significance of 6.3 standard deviations when other H couplings are fixed to their standard model values.

Signatures of a High Temperature QCD Transition in the Early Universe

Beyond-Standard-Model extensions of QCD could result in quark and gluon confinement occurring well above at temperature around the GeV scale. These models can also alter the order of the QCD phase transition. Therefore, the enhanced production of primordial black holes (PBHs) that can accompany the change in relativistic degrees of freedom at the QCD transition could favor the production of PBHs with mass scales smaller than the Standard Model QCD horizon scale. Consequently, and unlike PBHs associated with a standard GeV-scale QCD transition, such PBHs can account for all the dark matter abundance in the unconstrained asteroid-mass window. This links beyond-Standard-Model modifications of QCD physics over a broad range of unexplored temperature regimes (around 10-10^{3}  TeV) with microlensing surveys searching for PBHs. Additionally, we discuss implications of these models for gravitational wave experiments. We show that a first-order QCD phase transition at around 7 TeV is consistent with the Subaru Hyper-Suprime Cam candidate event, while a transition of around 70 GeV is consistent with OGLE candidate events and could also account for the claimed NANOGrav gravitational wave signal.

The Phenomenological Research on Higgs and Dark Matter in the Next-to-Minimal Supersymmetric Standard Model

The Z3-invariant next-to-minimal supersymmetric standard model (NMSSM) can provide a candidate for dark matter (DM). It can also be used to explain the hypothesis that the Higgs signal observed on the Large Hadron Collider (LHC) comes from the contribution of the two lightest CP-even Higgs bosons, whose masses are near 125 GeV. At present, XENON1T, LUX, and PandaX experiments have imposed very strict restrictions on direct collision cross sections of dark matter. In this paper, we consider a scenario that the observed Higgs signal is the superposition of two mass-degenerate Higgs in the Z3-invariant NMSSM and scan the seven-dimension parameter space composing of λ,κ,tanβ,μ,Ak,At,M1 via the Markov chain Monte Carlo (MCMC) method. We find that the DM relic density, as well as the LHC searches for sparticles, especially the DM direct detections, has provided a strong limit on the parameter space. The allowed parameter space is featured by a relatively small μ≤300 GeV and about tanβ∈(10,20). In addition, the DM is Higgsino-dominated because of |2κλ|>1. Moreover, the co-annihilation between χ˜10 and χ˜1± must be taken into account to obtain the reasonable DM relic density.

Inert Higgs Dark Matter for CDF II W-Boson Mass and Detection Prospects

The W-boson mass, which was recently measured at Fermilab with an unprecedented precision, suggests the presence of new multiplets beyond the standard model (SM). One of the minimal extensions of the SM is to introduce an additional scalar doublet in which the non-SM scalars can enhance W-boson mass via the loop corrections. On the other hand, with a proper discrete symmetry, the lightest new scalar in the doublet can be stable and play the role of a dark matter particle. We show that the inert two Higgs doublet model can naturally handle the new W-boson mass without violating other constraints and that the preferred dark matter mass is between 54 and 74 GeV. We identify three feasible parameter regions for the thermal relic density: the SA coannihilation, the Higgs resonance, and the SS→WW^{*} annihilation. We find that the first region can be fully tested by the High Luminosity Large Hadron Collider, the second region will be tightly constrained by direct detection experiments, and the third region could yield detectable GeV γ-ray and antiproton signals in the Galaxy that may have been observed by the Fermi Large Area Telescope and the Alpha Magnetic Spectrometer AMS-02 experiment.

Dark Photon Searches via Higgs Boson Production at the LHC and Beyond

Many scenarios beyond the standard model, aiming to solve long-standing cosmological and particle physics problems, suggest that dark matter might experience long-distance interactions mediated by an unbroken dark U(1) gauge symmetry, hence foreseeing the existence of a massless dark photon. Contrary to the massive dark photon, a massless dark photon can only couple to the standard model sector by means of effective higher dimensional operators. Massless dark photon production at colliders will then in general be suppressed at low energy by a UV energy scale, which is of the order of the masses of portal (messenger) fields connecting the dark and the observable sectors. A violation of this expectation is provided by dark photon production mediated by the Higgs boson, thanks to the non-decoupling Higgs properties. Higgs boson production at colliders, followed by the Higgs decay into a photon and a dark photon, provides then a very promising production mechanism for the dark photon discovery, being insensitive in particular regimes to the UV scale of the new physics. This decay channel gives rise to a peculiar signature characterized by a monochromatic photon with energy half the Higgs mass (in the Higgs rest frame) plus missing energy. We show how such resonant photon-plus-missing-energy signature can uniquely be connected to a dark photon production. Higgs boson production and decay into a photon and a dark photon as a source of dark photons is reviewed at the Large Hadron Collider, in light of the present bounds on the corresponding signature by the CMS and ATLAS collaborations. Perspectives for the dark photon production in Higgs-mediated processes at future e+e− colliders are also discussed.

Off-Shell Probes of the Higgs Yukawa Couplings: Light Quarks and Charm

We review the present status and the future prospects for the measurements of the Higgs Yukawa couplings to light quarks and charm. A special focus is given to new proposed off-shell probes, which offer promising and complementary opportunities to test light quark Yukawas in triboson final states. Additionally, a new off-shell strategy to test the charm Yukawa coupling in the final state with two bosons plus a charm and a jet is considered. First estimates for the HL-LHC and the FCC-hh sensitivities on the channel are presented, showing encouraging results.

The scientific potential and technological challenges of the High-Luminosity Large Hadron Collider program

We present an overview of the High-Luminosity (HL-LHC) program at the Large Hadron Collider (LHC), its scientific potential and technological challenges for both the accelerator and detectors. The HL-LHC program is expected to start circa 2027 and aims to increase the integrated luminosity delivered by the LHC by an order of magnitude at the collision energy of 14 TeV. This requires upgrades to the injector system, accelerator complex and luminosity levelling. The two experiments, ATLAS and CMS, require substantial upgrades to most of their systems in order to cope with the increased interaction rate, and much higher radiation levels than at the current LHC. We present selected examples based on novel ideas and technologies for applications at a hadron collider. Both experiments will replace their tracking systems. We describe the ATLAS pixel detector upgrade featuring novel tilted modules, and the CMS Outer Tracker upgrade with a new module design enabling use of tracks in the level-1 trigger system. CMS will also install state-of-the-art highly segmented calorimeter endcaps. Finally, we describe new picosecond precision timing detectors of both experiments. In addition, we discuss how the upgrades will enhance the physics performance of the experiments, and solve the computing challenges posed by the expected large data sets. The physics program of the HL-LHC is focused on precision measurements probing the limits of the Standard Model (SM) of particle physics and discovering new physics. We present a selection of studies that have been carried out to motivate the HL-LHC program. A central topic of exploration will be the characterization of the Higgs boson. The large HL-LHC data samples will extend the sensitivity of searches for new particles or new interactions whose existence has been hypothesized in order to explain shortcomings of the SM. Finally, we comment on the nature of large scientific collaborations.

m_{b} at m_{H}: The Running Bottom Quark Mass and the Higgs Boson

We present a new measurement of the bottom quark mass in the MS[over ¯] scheme at the renormalization scale of the Higgs boson mass from measurements of Higgs boson decay rates at the LHC: m_{b}(m_{H})=2.60_{-0.31}^{+0.36}  GeV. The measurement has a negligible theory uncertainty and excellent prospects to improve at the HL-LHC and a future Higgs factory. Confronting this result and m_{b}(m_{b}) from low-energy measurements and m_{b}(m_{Z}) from Z-pole data, with the prediction of the scale evolution of the renormalization group equations, we find strong evidence for the "running" of the bottom quark mass.

The THDMa Revisited

The THDMa is a new physics model that extends the scalar sector of the Standard Model by an additional doublet as well as a pseudoscalar singlet and allows for mixing between all possible scalar states. In the gauge-eigenbasis, the additional pseudoscalar serves as a portal to the dark sector, with a priori any dark matter spins states. The option where dark matter is fermionic is currently one of the standard benchmarks for the experimental collaborations, and several searches at the LHC constrain the corresponding parameter space. However, most current studies constrain regions in parameter space by setting all but 2 of the 12 free parameters to fixed values. In this work, we performed a generic scan on this model, allowing all parameters to float. We applied all current theoretical and experimental constraints, including bounds from current searches, recent results from B-physics, in particular Bs→Xsγ, as well as bounds from astroparticle physics. We identify regions in the parameter space which are still allowed after these were applied and which might be interesting for an investigation of current and future collider machines.

Exploration of Extended Higgs Sectors with Run-2 Proton–Proton Collision Data at the LHC

One doublet of complex scalar fields is the minimal content of the Higgs sector in order to achieve spontaneous electroweak symmetry breaking and, in turn, to generate the masses of fundamental particles in the Standard Model. However, several theories beyond the Standard Model predict a nonminimal Higgs sector and introduce additional singlets, doublets or even higher-order weak isospin representations, thereby yielding additional Higgs bosons. With its high proton–proton collision energy (13 TeV during Run-2), the Large Hadron Collider opens a new window towards the exploration of extended Higgs sectors. This review article summarises the current state-of-the-art experimental results recently obtained in searches for new neutral and charged Higgs bosons with a partial or full Run-2 dataset.

Fully Differential Higgs Boson Production to Third Order in QCD

We present the first fully differential predictions for the production cross section of a Higgs boson via the gluon fusion mechanism at next-to-next-to-next-to-leading order (N^{3}LO) in QCD perturbation theory. Differential distributions are shown for the two-photon final state produced by the decay of the Higgs boson for a realistic set of fiducial cuts. The N^{3}LO corrections exhibit complex features and are in part larger than the inclusive N^{3}LO corrections to the production cross section. Overall, we observe that the inclusion of the N^{3}LO QCD corrections significantly reduces the perturbative uncertainties and leads to a stabilization of the perturbative expansion.

Nearly Conformal Composite Higgs Model

We analyze a composite Higgs model based on the confining SU(3) gauge theory with N_{f}=8 Dirac fermions in the fundamental representation. This gauge theory has been studied on the lattice and shown to be well described by a dilaton effective field theory (EFT). Here we modify the EFT by assigning standard-model quantum numbers such that four of the composite pseudo-Nambu-Goldstone boson (pNGB) fields form the standard-model Higgs doublet, by coupling it to the top quark and by adding to the potential a term that triggers electroweak symmetry breaking. The model contains a pNGB Higgs boson, a set of heavier pNGBs, and an approximate dilaton in the same mass range. We study the phenomenology of the model and discuss the amount of tuning required to ensure consistency with current direct and indirect bounds on new physics, highlighting the role of the dilaton field.

Dark Matter Constraints and the Neutralino Sector of the scNMSSM

The neutralino sector of the semi-constrained next-to-minimal supersymmetric standard model is explored under recent experimental constraints, with special attention to dark matter (DM) limits. The effects of the upper and lower bounds of dark matter relic density and recent direct detection constraints on spin-independent and -dependent cross-sections are thoroughly analyzed. Particularly, we show which regions of the parameter space are ruled out due to the different dark matter constraints and the corresponding model-specific parameters: λ,κ,Aλ, and Aκ. We analyze all annihilation and co-annihilation processes (with heavier neutralinos and charginos) that contribute to the dark matter relic density. The mass components of the dark matter candidate, the lightest neutralino χ˜10, are studied, and the decays of heavy neutralinos and charginos, especially χ˜20 and χ˜1+, into the lightest neutralino are examined. We impose semi-universal boundary conditions at the Grand Unified Theory scale, and require a moderate range of tanβ≲10. We find that the allowed parameter space is associated with a heavy mass spectrum in general and that the lightest neutralino is mostly Higgsino with a mass range that resides mostly between 1000 and 1500 GeV. However, smaller mass values can be achieved if the DM candidate is bino-like or singlino-like.

Sub-TeV H^{+} Boson Production as Probe of Extra Top Yukawa Couplings

We suggest searching for the charged Higgs boson at the Large Hadron Collider (LHC) via cg→bH^{+}→btb[over ¯]. In the general two Higgs doublet model, extra top Yukawa couplings ρ_{tc} and ρ_{tt} can drive the disappearance of antimatter from the Universe, while c[over ¯]bH^{+} and t[over ¯]bH^{+} couple with strength ρ_{tc}V_{tb} and ρ_{tt}V_{tb}, respectively. For ρ_{tc},ρ_{tt}∼0.5, and m_{H^{+}}∼300-500  GeV, evidence could emerge from LHC run 2 data at hand and discovery by adding run 3 data in the near future.

The Higgs Field and Early Universe Cosmology: A (Brief) Review

We review and discuss recent work exploring the implications of the Higgs field for early universe cosmology, and vice versa. Depending on the model under consideration, the Higgs may be one of a few scalar fields determining the evolution and fate of the Universe, or the Higgs field may be connected to a rich sector of scalar moduli with complicated dynamics. In particular, we look at the potential consequences of the Higgs field for inflation and its predictions, for the (meta)stability of the Standard Model vacuum, and for the existence of dynamical selection mechanisms in the landscape.

CP Properties of Higgs Boson Interactions with Top Quarks in the tt[over ¯]H and tH Processes Using H→γγ with the ATLAS Detector

A study of the charge conjugation and parity (CP) properties of the interaction between the Higgs boson and top quarks is presented. Higgs bosons are identified via the diphoton decay channel (H→γγ), and their production in association with a top quark pair (tt[over ¯]H) or single top quark (tH) is studied. The analysis uses 139  fb^{-1} of proton-proton collision data recorded at a center-of-mass energy of sqrt[s]=13  TeV with the ATLAS detector at the Large Hadron Collider. Assuming a CP-even coupling, the tt[over ¯]H process is observed with a significance of 5.2 standard deviations. The measured cross section times H→γγ branching ratio is 1.64_{-0.36}^{+0.38}(stat)_{-0.14}^{+0.17}(sys)  fb, and the measured rate for tt[over ¯]H is 1.43_{-0.31}^{+0.33}(stat)_{-0.15}^{+0.21}(sys) times the Standard Model expectation. The tH production process is not observed and an upper limit on its rate of 12 times the Standard Model expectation is set. A CP-mixing angle greater (less) than 43 (-43)° is excluded at 95% confidence level.

Search for Heavy Higgs Bosons Decaying into Two Tau Leptons with the ATLAS Detector Using pp Collisions at sqrt[s]=13 TeV

A search for heavy neutral Higgs bosons is performed using the LHC Run 2 data, corresponding to an integrated luminosity of 139  fb^{-1} of proton-proton collisions at sqrt[s]=13  TeV recorded with the ATLAS detector. The search for heavy resonances is performed over the mass range 0.2-2.5 TeV for the τ^{+}τ^{-} decay with at least one τ-lepton decaying into final states with hadrons. The data are in good agreement with the background prediction of the standard model. In the M_{h}^{125} scenario of the minimal supersymmetric standard model, values of tanβ>8 and tanβ>21 are excluded at the 95% confidence level for neutral Higgs boson masses of 1.0 and 1.5 TeV, respectively, where tanβ is the ratio of the vacuum expectation values of the two Higgs doublets.

Cornering Spontaneous CP Violation with Charged-Higgs-Boson Searches

Decades of precision measurements have firmly established the Kobayashi-Maskawa phase as the dominant source of the charge-parity (CP) violation observed in weak quark decays. However, it is still unclear whether CP violation is explicitly encoded in complex Yukawa matrices or instead stems from spontaneous symmetry breaking with underlying CP-conserving Yukawa and Higgs sectors. Here we study the latter possibility for the case of a generic two-Higgs-doublet model. We find that theoretical constraints limit the ratio t_{β} of the vacuum expectation values (vevs) to the range 0.22≤t_{β}≤4.5 and imply the upper bounds M_{H^{±}}≤435  GeV, M_{H_{2}^{0}}≤485  GeV and M_{H_{3}^{0}}≤545  GeV for the charged and extra neutral Higgs masses. We derive lower bounds on charged-Higgs couplings to bottom quarks which provide a strong motivation to study the nonstandard production and decay signatures pp→qbH^{±}(→q^{'}b) with all flavors q,q^{'}=u, c, t in the search for the charged Higgs boson. We further present a few benchmark scenarios with interesting discovery potential in collider analyses.

Nonresonant Searches for Axionlike Particles at the LHC

We propose a new collider probe for axionlike particles (ALPs), and more generally for pseudo-Goldstone bosons: nonresonant searches that take advantage of the derivative nature of their interactions with Standard Model particles. ALPs can participate as off shell mediators in the s channel of 2→2 scattering processes at colliders like the LHC. We exemplify the power of this novel type of search by deriving new limits on ALP couplings to gauge bosons via the processes pp→ZZ, pp→γγ, and pp→jj using run 2 CMS public data, probing previously unexplored areas of the ALP parameter space. In addition, we propose future nonresonant searches involving the ALP coupling to other electroweak bosons and/or the Higgs particle.

Real-time data analysis model at LHC and connections to other experiments and fields

With the upcoming increase of proton-proton collision rates at the Large Hadron Collider (LHC) experiments, and the corresponding increase of data volumes, real-time analysis becomes a key ingredient to be able to analyse and select the interesting data within the available computing resources. In this talk I will review the main features of the techniques followed by the ATLAS, CMS and LHCb experiments. Similar challenges have to be faced in other fields, such as astronomy and cosmology, and I will comment about them.