Local operators are the basic observables in quantum field theory which encode the physics observed by a local experimentalist. However, when gravity is dynamical, diffeomorphism symmetries are gauged which apparently obstruct a sensible definition of local operators, as different locations in spacetime are connected by these gauged symmetries. This consideration brings in the puzzle of reconciling our empirical world with quantum gravity. Intuitively, this puzzle can be avoided using relatively defined observables when there exists a natural reference system such as a distribution of galaxies in our Universe. Nevertheless, this intuition is classical as the rods and clock defined in this way may also have quantum fluctuations, so it is not a priori clear if it can be realized in the quantum regime. In this paper, we provide an affirmative answer to this question. Interestingly, we notice that the quantum fluctuations of the reference system are in fact essential for the realization of the above intuition in the quantum regime.

United States

Hao Geng

Quantum rods and clock in a gravitational universe

The multiplicities of positive and negative pions, kaons, and unidentified hadrons produced in deep-inelastic scattering are measured in bins of the Bjorken scaling variable <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math>, the relative virtual-photon energy <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>y</mi></math>, and the fraction of the virtual-photon energy transferred to the final-state hadron <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>z</mi></math>. Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam of both electric charges and a liquid hydrogen target. These measurements cover the kinematic domain with photon virtuality <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>Q</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>&gt;</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><mo stretchy="false">(</mo><mrow><mi>GeV</mi><mo>/</mo><mi>c</mi><msup><mrow><mo stretchy="false">)</mo></mrow><mrow><mn>2</mn></mrow></msup></mrow></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>0.004</mn><mo>&lt;</mo><mi>x</mi><mo>&lt;</mo><mn>0.4</mn></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>0.1</mn><mo>&lt;</mo><mi>y</mi><mo>&lt;</mo><mn>0.7</mn></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>0.2</mn><mo>&lt;</mo><mi>z</mi><mo>&lt;</mo><mn>0.85</mn></math>, in accordance with the kinematic domain used in earlier published COMPASS multiplicity measurements with an isoscalar target. The calculation of radiative corrections was improved by using the Monte Carlo generator djangoh, which results in up to 12% larger corrections in the low-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math> region.

G.D. Alexeev

Italy

M.G. Alexeev

C. Alice

A. Amoroso

V. Andrieux

V. Anosov

Czechia

K. Augsten

Poland

W. Augustyniak

Portugal

C.D.R. Azevedo

B. Badelek

Germany

J. Barth

R. Beck

J. Beckers

France

Y. Bedfer

CERN

J. Bernhard

M. Bodlak

F. Bradamante

A. Bressan

Taiwan

W.C. Chang

C. Chatterjee

M. Chiosso

S.U. Chung

A. Cicuttin

P.M.M. Correia

M.L. Crespo

D. D’Ago

S. Dalla Torre

India

S.S. Dasgupta

S. Dasgupta

F. Delcarro

I. Denisenko

O. Yu. Denisov

S.V. Donskov

Japan

N. Doshita

Ch. Dreisbach

W. Dünnweber

Armenia

R.R. Dusaev

D. Ecker

D. Eremeev

P. Faccioli

M. Faessler

M. Finger

H. Fischer

K.J. Flöthner

W. Florian

J.M. Friedrich

V. Frolov

L.G. Garcia Ordòñez

O.P. Gavrichtchouk

S. Gerassimov

J. Giarra

D. Giordano

A. Grasso

A. Gridin

M. Grosse Perdekamp

B. Grube

M. Grüner

A. Guskov

P. Haas

D. von Harrach

M. Hoffmann

N. d’Hose

C.Y. Hsieh

S. Ishimoto

A. Ivanov

T. Iwata

V. Jary

R. Joosten

E. Kabuß

F. Kaspar

A. Kerbizi

B. Ketzer

A. Khatun

G.V. Khaustov

F. Klein

J.H. Koivuniemi

V.N. Kolosov

K. Kondo Horikawa

I. Konorov

A. Yu. Korzenev

A.M. Kotzinian

O.M. Kouznetsov

A. Koval

Z. Kral

F. Kunne

K. Kurek

R.P. Kurjata

K. Lavickova

S. Levorato

Y.S. Lian

Israel

J. Lichtenstadt

P.J. Lin

R. Longo

V.E. Lyubovitskij

A. Maggiora

N. Makke

G.K. Mallot

A. Maltsev

A. Martin

Multiplicities of positive and negative pions, kaons, and unidentified hadrons from deep-inelastic scattering of muons off a liquid hydrogen target

In this work, nontrivial analytic structure of the quark propagator is discussed for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>B</mi></mrow></math>-meson inclusive decays. Attributed to invalidity of the standard Källén-Lehman spectral representation, complex conjugate poles alter the evaluation of decay rates, which lead to violation of quark-hadron duality. As phenomenological observables, widths in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo stretchy="false">→</mo><msub><mi>X</mi><mi>c</mi></msub><mo>ℓ</mo><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover></math> decay as well as the lifetime of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>d</mi><mn>0</mn></msubsup></math> meson are discussed. In the presence of the mentioned nonanalytical contributions, the possibility for resolving the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><msub><mi>V</mi><mrow><mi>c</mi><mi>b</mi></mrow></msub><mo stretchy="false">|</mo></math> puzzle is addressed. It is demonstrated that there exists a parameter region, which explains <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><msub><mi>V</mi><mrow><mi>c</mi><mi>b</mi></mrow></msub><mo stretchy="false">|</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>d</mi><mn>0</mn></msubsup></math>-meson lifetime simultaneously within <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1</mn><mi>σ</mi></mrow></math> via the complex conjugate poles from a charm quark.

China

Jinglong Zhu

Hiroyuki Umeeda

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo stretchy="false">→</mo><msub><mi>X</mi><mi>c</mi></msub><mo>ℓ</mo><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover></math> decay as a probe of complex conjugate poles

We introduce a new dark matter detection mechanism, dark matter internal pair production (DIPP), to detect dark matter candidates at beam dump facilities. When energetic dark matter scatters in a material, it can create a lepton-antilepton pair by exchanging a virtual photon with the nucleus, akin to the neutrino trident process. We demonstrate this process for dark matter coupled to dark photons in experiments such as DarkQuest, SBND, and DUNE ND. Since the lepton-antilepton pair carries a significant fraction of dark matter energy, it can be clearly distinguished from backgrounds. Utilizing the above features, we show that DIPP is highly effective at probing various dark matter models, particularly at DUNE ND and DarkQuest, by searching for electron-positron and muon-antimuon signatures. At DUNE ND, we find that the sensitivity of DIPP extends over a larger parameter space than the existing limits from electron and nuclear recoil. Additionally, we explore a scenario where dark sector couplings involve quarks and muons only, demonstrating that DIPP can probe a wide variety of dark matter models with different final states.

Bhaskar Dutta

Aparajitha Karthikeyan

Mudit Rai

Hyunyong Kim

Dark Matter Internal Pair Production: A Novel Direct Detection Mechanism

The validity range of the time-honored effective range expansion can be very limited due to the presence of a left-hand cut close to the two-particle threshold. Such a left-hand cut arises in the two-particle interaction involving a light particle exchange with a small mass or a mass slightly heavier than the mass difference of the two particles, identified as a long-range force, a scenario encountered in a broad range of systems. This can hinder a precise extraction of low-energy scattering observables and resonance poles. To address this issue, we propose a new parametrization for the low-energy scattering amplitude that accounts for the left-hand cut. The parametrization is like a Padé approximation but with nonanalytic terms from the left-hand cut and can be regarded as an extension of the effective range expansion. This parametrization is versatile and applicable to a broad range of systems with Yukawa-type interactions, including particle, hadronic, nuclear, cold atom, and quantum gas systems. In particular, it should be invaluable in understanding various near-threshold hadron resonances. As byproducts, we also show that the parametrization can be used to extract the couplings of the exchanged particle to the scattering particles, and derive expressions for amplitude zeros caused by the interplay between the short- and long-range interactions.

Meng-Lin Du

Feng-Kun Guo

Bing Wu

Effective-Range Expansion with a Long-Range Force

To search for $$\beta \beta 0\nu $$ decay with unprecedented sensitivity, the R2D2 collaboration is developing a radial time projection chamber with a fiducial mass of half a tonne of $$^{136}$$ Xe at high pressure. The various approaches implemented to eliminate the radioactive background are presented in terms of detector design, topological recognition of interactions, and event energy reconstruction. The developed tools enable the disentangling of the sought-after signal from the background. The projected sensitivity after ten years of data taking yields a half-life limit exceeding $$10^{27}$$ years, along with a constraint on the effective neutrino mass $$m_{\beta \beta }$$ that could cover a large fraction of the inverted mass hierarchy region, depending on the final experimental background.

R. Bouet

J. Busto

A. Cadiou

P. Charpentier

D. Charrier

M. Chapellier

A. Dastgheibi-Fard

F. Druillole

P. Hellmuth

C. Jollet

Slovakia

J. Kaizer

I. Kontul

P. Le Ray

M. Gros

P. Lautridou

M. Macko

A. Meregaglia

F. Piquemal

P. Povinec

M. Roche

Simulation of a radial TPC for the detection of neutrinoless double beta decay

The proposal of a rapid sign-switching cosmological constant in the late universe, mirroring a transition from anti-de Sitter (AdS) to de Sitter (dS) space, has significantly improved the fit to observational data and provides a compelling framework for ameliorating major cosmological tensions, such as the $\textit{H}$ and $\textit{S}$ tensions. An attractive theoretical realisation that accommodates the AdS → dS transition relies on the Casimir forces of fields inhabiting the bulk of a 5-dimensional (5-dim) set up. Among the fields characterising the dark sector, there is a real scalar field $\textit{ϕ}$ endowed with a potential holding two local minima with very small difference in vacuum energy and bigger curvature (mass) of the lower one. Shortly after the false vacuum tunnels to its true vacuum state, $\textit{ϕ}$ becomes more massive and its contribution to the Casimir energy becomes exponentially suppressed. The tunneling process then changes the difference between the total number of fermionic and bosonic degrees of freedom contributing to the quantum corrections of the vacuum energy, yielding the AdS → dS transition. We investigate the properties of this theoretical realisation to validate its main hypothesis and characterise free parameters of the model. We adopt the Coleman-de Luccia formalism for calculating the transition probability within the thin-wall approximation. We show that the Euclidean bounce configuration that drives the transition between $\textit{ϕ}$ vacua has associated at least a sixth order potential. We also show that distinctive features of the required vacuum decay to accommodate the AdS $\textit{→}$ dS transition are inconsistent with a 5-dim non-compact description of the instanton, for which the bounce is $\textit{O}$(5) symmetric, and instead call for a 5-dim instanton with a compact dimension, for which the bounce is $\textit{O}$(4) × U(1) symmetric.

Luis Anchordoqui

Thailand

Ignatios Antoniadis

Daniele Bielli

Auttakit Chatrabhuti

Hiroshi Isono

Thin-wall vacuum decay in the presence of a compact dimension meets the $\textit{H}$

We study discrete series representations of SL(2, $\textit{ℝ}$) with half-integer scaling dimension ∆. At the classical level, we show that these UIRs are realised in the space of mode solutions of spinor fields with $\textit{imaginary mass parameters}$ on a fixed two-dimensional de Sitter, dS , background. Upon such tuning of the mass, the field develops a fermionic shift symmetry that we characterise. We show that in the Euclidean section this manifests itself in the presence of zero-modes which preclude the definition of a Hadamard two-point function for these UIRs. We propose a Euclidean procedure to deal with the zero-modes, define a two-point function with the right singularity structure, and analyse its late-time behaviour. We end this note by proposing two interacting theories containing the fermionic discrete series in their spectrum.

United Kingdom

Belgium

Vasileios Letsios

Ben Pethybridge

Alan Fukelman

Quite discrete for a fermion

Axion-like particles can couple to Standard Model gluons, electroweak gauge bosons, and massive fermions. A future multi-TeV muon collider provides a favorable environment to probe axion-like particles through multiple production channels, including vector boson fusion via electroweak gauge boson couplings and the top-associated production mediated by direct fermionic couplings. Motivated by the quality issue of the QCD axion, we focus on axion-like particles with masses and decay constants around the TeV scale. We explore how different axion-like particle couplings shape its production and decay modes, revealing a rich and intricate phenomenological landscape.

So Chigusa

Sudhakantha Girmohanta

Yuichiro Nakai

Yufei Zhang

Interplay of ALP couplings at a muon collider

$\textit{A}$-type Little String Theories (LSTs) are engineered from parallel M5-branes on a circle $$ {\mathbbm{S}}_{\perp}^1 $$ , probing a transverse ℝ /ℤ background. Below the scale of the radius of $$ {\mathbbm{S}}_{\perp}^1 $$ , these theories resemble a circular quiver gauge theory with $\textit{M}$ nodes of gauge group U($\textit{N}$) and matter in the bifundamental representation (or adjoint in the case of $\textit{M}$ = 1). In this paper, we study these LSTs in the presence of a surface defect, which is introduced through the action of a ℤ orbifold that breaks the gauge groups into [U(1)] . We provide a combinatoric expression for the non-perturbative BPS partition function for this system. This form allows us to argue that a number of non-perturbative symmetries, that have previously been established for the LSTs, are preserved in the presence of the defect. Furthermore, we discuss the Nekrasov-Shatashvili (NS) limit of the defect partition function: focusing in detail on the case ($\textit{M}$, $\textit{N}$) = (1, 2), we analyse two distinct proposals made in the literature. We unravel an algebraic structure that is responsible for the cancellation of singular terms in the NS limit, which we generalise to generic ($\textit{M}$, $\textit{N}$). In view of the dualities of higher dimensional gauge theories to quantum many-body systems, we provide indications that our combinatoric expression for the defect partition are useful in constructing and analysing quantum integrable systems in the future.

Baptiste Filoche

Stefan Hohenegger

Taro Kimura

Surface defects in $\textit{A}$-type Little String Theories