We study the new $Z'$ boson as a portal for the production of Higgs bosons $h_0$ and $H_0$ predicted by the Bestest Little Higgs Model through Higgs-strahlung processes $\mu^+\mu^- \to (Z, Z') \to Zh_0, ZH_0$ . We focus on the resonant and nonresonant effects of the $Zh_0, ZH_0$ signals. In our analysis, we consider the center-of-mass energies of $\sqrt{s}=3, 4, 6, 10, 30$ TeV and integrated luminosities of ${\cal{L}}=2, 4, 6, 10, 30$ ${ {\rm{ab}}^{-1}}$ projected for a future muon collider. The possibility of performing precision measurements for Higgs bosons $h_0$ and $H_0$ is very promising for the future muon collider. Furthermore, our results may be useful to the High Energy Physics community. Complementarily, we generate and provide the Feynman rules necessary for studying processes $\mu^+\mu^- \to (Z, Z') \to Zh_0, ZH_0$ .

New $\textit{Z}$' boson of the bestest little Higgs model as a portal to signatures of Higgs bosons $\textit{h}$ $_{0}$ and $\textit{H}$ $_{0}$ at the future muon collider

We employ an equal-velocity quark combination model to study anisotropic flows <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>2</mn></msub><mo>,</mo><mo> </mo><msub><mi>v</mi><mn>3</mn></msub></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>4</mn></msub></math> of identified hadrons at midrapidity in heavy-ion collisions at Relativistic Heavy Ion Collider energies. Under the equal-velocity combination mechanism of constituent quarks at hadronization, we build analytical formulas of anisotropic flows of hadrons in terms of those of quarks just before hadronization. We systematically analyze the contribution of higher-order flows of quarks, and show how simple formulas of <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>2</mn></msub><mo>,</mo><mo> </mo><msub><mi>v</mi><mn>3</mn></msub></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>4</mn></msub></math> of identified hadrons with the desired precision can be obtained by neglecting the small contribution of higher-order flows of quarks. We systematically test these simple formulas of hadronic flows by the experimental data of <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>2</mn></msub><mo>,</mo><mo> </mo><msub><mi>v</mi><mn>3</mn></msub></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>4</mn></msub></math> of identified hadrons <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>ϕ</mi><mo>,</mo><mo> </mo><mi mathvariant="normal">Λ</mi><mo>,</mo><mo> </mo><msup><mi mathvariant="normal">Ξ</mi><mo>−</mo></msup><mo>,</mo><mo> </mo><msup><mi mathvariant="normal">Ω</mi><mo>−</mo></msup><mo>,</mo><mo> </mo><mover accent="true"><mi mathvariant="normal">Λ</mi><mo>¯</mo></mover><mo>,</mo><mo> </mo><msup><mover accent="true"><mi mathvariant="normal">Ξ</mi><mo>¯</mo></mover><mo>+</mo></msup><mo>,</mo><mo> </mo><msup><mover accent="true"><mi mathvariant="normal">Ω</mi><mo>¯</mo></mover><mo>+</mo></msup><mo>,</mo><mo> </mo><mi>p</mi></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><mover accent="true"><mi>p</mi><mo>¯</mo></mover></math> in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Au</mi><mo>+</mo><mi>Au</mi></mrow></math> collisions at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>19.6</mn></mrow></math>, 54.4, and 200 GeV, and we find that the equal-velocity quark combination model can well describe the measured <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>2</mn></msub><mo>,</mo><mo> </mo><msub><mi>v</mi><mn>3</mn></msub></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>v</mi><mn>4</mn></msub></math> of identified hadrons in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Au</mi><mo>+</mo><mi>Au</mi></mrow></math> collisions at those collision energies. We further study the obtained anisotropic flows of quarks and find two scaling properties which can be qualitatively understood by the hydrodynamic evolution of the thermal quark medium produced in relativistic heavy-ion collisions.

China

Anisotropic flows of identified hadrons in the equal-velocity quark combination model at energies available at the BNL Relativistic Heavy Ion Collider

The low-energy, finite-volume spectrum of the two-nucleon system at a quark mass corresponding to a pion mass of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>π</mi></mrow></msub><mo>≈</mo><mn>806</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math> is studied with lattice quantum chromodynamics (LQCD) using variational methods. The interpolating-operator sets used in [Variational study of two-nucleon systems with lattice QCD, <a href="http://dx.doi.org/10.1103/PhysRevD.107.094508">Phys. Rev. D 107, 094508 (2023)</a>.] are extended by including a complete basis of local hexaquark operators, as well as plane-wave dibaryon operators built from products of both positive- and negative-parity nucleon operators. Results are presented for the isosinglet and isotriplet two-nucleon channels. In both channels, noticeably weaker variational bounds on the lowest few energy eigenvalues are obtained from operator sets which contain only hexaquark operators or operators constructed from the product of two negative-parity nucleons, while other operator sets produce low-energy variational bounds which are consistent within statistical uncertainties. The consequences of these studies for the LQCD understanding of the two-nucleon spectrum are investigated.

United States

Spain

Constraints on the finite volume two-nucleon spectrum at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>π</mi></msub><mo>≈</mo><mn>806</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math>

Neutrino propagation in the Galactic and extragalactic magnetic fields is considered. We extend an approach developed in [A. Popov and A. Studenikin, Neutrino eigenstates and flavour, spin and spin-flavour oscillations in a constant magnetic field, <a href="http://dx.doi.org/10.1140/epjc/s10052-019-6657-z">Eur. Phys. J. C 79, 144 (2019)</a>.] to describe neutrino flavor and spin oscillations using wave packets. The evolution equations for the neutrino wave packets in a uniform and nonuniform magnetic fields are derived. The analytical expressions for neutrino flavor and spin oscillations probabilities accounting for damping due to the wave packet separation are obtained for the case of a uniform magnetic field. It is shown that terms in the flavor oscillations probabilities that depend on the magnetic field strength are characterized by two coherence lengths. One of the coherence lengths coincides with the coherence length for neutrino oscillations in vacuum, while the second one is proportional to the cube of the average neutrino momentum <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>p</mi><mn>0</mn><mn>3</mn></msubsup></math>. The probabilities of flavor and spin oscillations are calculated numerically for neutrino interacting with the nonuniform Galactic magnetic field. It is shown that oscillations on certain frequencies are suppressed on the Galactic scale due to the neutrino wave packets separation. The flavor compositions of high-energy neutrino flux coming from the Galactic center and ultra-high energy neutrinos from an extragalactic source are calculated accounting for neutrino interaction with the magnetic field and decoherence due to the wave packet separation. It is shown that for neutrino magnetic moments <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>13</mn></mrow></msup><msub><mi>μ</mi><mi>B</mi></msub></math> and larger these flavor compositions significantly differ from ones predicted by the vacuum neutrino oscillations scenario.

Russia

High-energy neutrinos flavor composition as a probe of neutrino magnetic moments

New insights from the Dark Energy Spectroscopic Instrument (DESI) 2024 baryon acoustic oscillations (BAO) data, in conjunction with cosmic microwave background (CMB) and Type Ia supernova (SN) data, suggest that dark energy may not be a cosmological constant. In this work, we investigate the cosmological implications of holographic dark energy (HDE) and interacting holographic dark energy (IHDE) models, utilizing CMB, DESI BAO, and SN data. By considering the combined DESI BAO and SN data, we determine that in the IHDE model, the parameter $$c > 1$$ and the dark-energy equation of state $\textit{w}$ does not cross $$-1$$ at the $$1\sigma $$ confidence level, whereas in the HDE model, it marginally falls below this threshold. Upon incorporating CMB data, we observe that in the HDE model, the parameter $$c < 1$$ and $\textit{w}$ crosses $$-1$$ at a level beyond $$10\sigma $$ . Conversely, for the IHDE model, the likelihood of $\textit{w}$ crossing $$-1$$ is considerably diminished, implying that the introduction of interaction within the HDE model could potentially resolve or mitigate the cosmic big rip conundrum. Furthermore, our analysis reveals that the HDE and IHDE models are statistically as viable as the $$\Lambda $$ CDM model when assessing Bayesian evidence with DESI BAO data combined with SN data. However, when CMB data are added, the HDE and IHDE models are significantly less favored than the $$\Lambda $$ CDM model. Our findings advocate for further exploration of the HDE and IHDE models using forthcoming, more precise late-universe observations.

Revisiting holographic dark energy after DESI 2024

This paper presents the reconstruction of missing transverse momentum ( $$p_{\text {T}}^{\text {miss}}$$ ) in proton–proton collisions, at a center-of-mass energy of 13 TeV. This is a challenging task involving many detector inputs, combining fully calibrated electrons, muons, photons, hadronically decaying $$\tau $$ -leptons, hadronic jets, and soft activity from remaining tracks. Possible double counting of momentum is avoided by applying a signal ambiguity resolution procedure which rejects detector inputs that have already been used. Several $$p_{\text {T}}^{\text {miss}}$$ ‘working points’ are defined with varying stringency of selections, the tightest improving the resolution at high pile-up by up to 39% compared to the loosest. The $$p_{\text {T}}^{\text {miss}}$$ performance is evaluated using data and Monte Carlo simulation, with an emphasis on understanding the impact of pile-up, primarily using events consistent with leptonic $\textit{Z}$ decays. The studies use $$140~\text {fb}^{-1}$$ of data, collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. The results demonstrate that $$p_{\text {T}}^{\text {miss}}$$ reconstruction, and its associated significance, are well understood and reliably modelled by simulation. Finally, the systematic uncertainties on the soft $$p_{\text {T}}^{\text {miss}}$$ component are calculated. After various improvements the scale and resolution uncertainties are reduced by up to $$76\%$$ and $$51\%$$ , respectively, compared to the previous calculation at a lower luminosity.

France

Norway

Germany

Morocco

Israel

Italy

United Kingdom

Poland

Türkiye

Romania

Switzerland

Azerbaijan

Canada

Sweden

Japan

Greece

Czechia

Taiwan

South Africa

Chile

Argentina

Brazil

Portugal

The performance of missing transverse momentum reconstruction and its significance with the ATLAS detector using 140 $$\hbox {fb}^{-1}$$ of $$\sqrt{s}=13$$ TeV $\textit{pp}$ collisions

The first and second laws of thermodynamics should lead to a consistent scenario for discussing the cosmological constant problem. In the present study, to establish such a thermodynamic scenario, cosmological equations in a flat Friedmann–Lemaître–Robertson–Walker universe were derived from the first law, using an arbitrary entropy $$S_{H}$$ on a cosmological horizon. Then, the cosmological equations were formulated based on a general formulation that includes two extra driving terms, $$f_{\Lambda }(t)$$ and $$h_{\text {B}}(t)$$ , which are usually used for, e.g., time-varying $$\Lambda (t)$$ cosmology and bulk viscous cosmology, respectively. In addition, thermodynamic constraints on the two terms are examined using the second law of thermodynamics, extending a previous analysis (Komatsu in Phys. Rev. D 99:043523, 2019). It is found that a deviation $$S_{\Delta }$$ of $$S_{H}$$ from the Bekenstein–Hawking entropy plays important roles in the two terms. The second law should constrain the upper limits of $$f_{\Lambda }(t)$$ and $$h_{\text {B}}(t)$$ in our late Universe. The orders of the two terms are likely consistent with the order of the cosmological constant $$\Lambda _{\text {obs}}$$ measured by observations. In particular, when the deviation $$S_{\Delta }$$ is close to zero, $$h_{\text {B}}(t)$$ and $$f_{\Lambda }(t)$$ should reduce to zero and a constant value (consistent with the order of $$\Lambda _{\text {obs}}$$ ), respectively, as if a consistent and viable scenario could be obtained from thermodynamics.

Cosmological scenario based on the first and second laws of thermodynamics: thermodynamic constraints on a generalized cosmological model

The system of light electroweakinos and heavy squarks gives rise to one of the most challenging signatures to detect at the LHC. It consists of missing transverse energy recoiled against a few hadronic jets originating either from QCD radiation or squark decays. The analysis generally suffers from the large irreducible $$Z + \textrm{jets}$$ ( $$Z \rightarrow \nu {\bar{\nu }}$$ ) background. In this study, we explore Machine Learning (ML) methods for efficient signal/background discrimination. Our best attempt uses both reconstructed (jets, missing transverse energy, etc.) and low-level (particle-flow) objects. We find that the discrimination performance improves as the $$p_\textrm{T}$$ threshold for soft particles is lowered from 10 to 1 GeV, at the expense of larger systematic uncertainty. In many cases, the ML method provides a factor two enhancement in $$S/\sqrt{S+B}$$ from a simple kinematical selection. The sensitivity on the squark-elecroweakino mass plane is derived with this method, assuming the Run-3 and HL-LHC luminosities. Moreover, we investigate the relations between input features and the network’s classification performance to reveal the physical information used in the background/signal discrimination process.

Machine learning electroweakino production

Tiny Lorentz invariance violation (LIV) effects, potentially arising from quantum gravity-induced spacetime structures, may also manifest in the proton sector, offering a plausible pathway to test Planck-scale physics through high-energy cosmic phenomena. Our analysis reveals that even minuscule LIV effects in the proton sector can significantly elevate the photon threshold energy for photopion production to $${\mathcal {O}}$$ (0.1 to $$10^3$$ eV), orders of magnitude higher than in Lorentz-symmetric scenarios. Consequently, protons in ultra-high-energy cosmic rays (UHECRs) can propagate for very long distances without significant energy loss via photopion interactions with cosmic microwave background (CMB) photons. This suppression of attenuation may provide a plausible explanation for the observed cosmic-ray events exceeding the Greisen–Zatsepin–Kuzmin (GZK) cutoff energy. We further demonstrate that when both leading-order and next-to-leading-order LIV effects are considered, higher-order LIV contributions induce discontinuous transitions in the GZK cutoff energy spectrum. Observations of proton-dominated UHECRs beyond the GZK threshold could provide constraints the LIV energy scale. Offering insights into the ultraviolet regime of LIV theories near the Planck scale, UHECRs may serve as a sensitive probe of LIV and provide a means to test quantum gravity predictions by constraining deviations from Lorentz symmetry in extreme-energy regimes.

Ultra high energy cosmic rays in light of the Lorentz invariance violation effects within the proton sector

In any conformally invariant gravitational theory, the space of exact solutions is greatly enlarged. Therefore, we cannot exclude the Weyl’s conformal invariance to be spontaneously broken to spherically symmetric vacuum solutions that exclude the spacetime region inside the black hole’s event horizon from our Universe. We baptize these solutions $\textit{conformalons}$. It turns out that for all such spacetimes nothing can reach the Schwarzschild event horizon in a finite amount of proper time for conformally coupled “massive” particles, or finite values of the affine parameter for massless particles. Therefore, for such vacuum solutions the surface $$r = 2 M$$ becomes an asymptotic region of the Universe. As a general feature, all conformalons show a gravitational blueshift instead of a gravitational redshift at the unattainable Schwarzschild event horizon, hence avoiding the Trans-Planckian problem in the Hawking evaporation process. Unexpectedly, the Hawking’s temperature of the conformalons turns out to be negative and the thermodynamic interpretation leads us to speculate about a possible maximum energy state of the Hawking radiation. Contrary to the Schwarzschild spacetime, for the conformalons the gravitational collapse consists of matter that falls down forever towards the Schwarzschild horizon without ever reaching it. Hence, the annihilation process between the matter and Hawking’s negative energy particles takes place outside the surface at $$r = 2 M$$ . Finally, the information is not lost in the whole process of singularity-free collapse and evaporation.