Signal Of New Physics Research Articles

Future Circular Colliders

After 10 years of physics at the Large Hadron Collider (LHC), the particle physics landscape has greatly evolved. Today, a staged Future Circular Collider (FCC), consisting of a luminosity-frontier highest-energy electron–positron collider (FCC-ee) followed by an energy-frontier hadron collider (FCC-hh), promises the most far-reaching physics program for the post-LHC era. FCC-ee will be a precision instrument used to study the Z, W, Higgs, and top particles, and will offer unprecedented sensitivity to signs of new physics. Most of the FCC-ee infrastructure could be reused for FCC-hh, which will provide proton–proton collisions at a center-of-mass energy of 100 TeV and could directly produce new particles with masses of up to several tens of TeV. This collider will also measure the Higgs self-coupling and explore the dynamics of electroweak symmetry breaking. Thermal dark matter candidates will be either discovered or conclusively ruled out by FCC-hh. Heavy-ion and electron–proton collisions (FCC-eh) will further contribute to the breadth of the overall FCC program. The integrated FCC infrastructure will serve the particle physics community through the end of the twenty-first century. This review combines key contents from the first three volumes of the FCC Conceptual Design Report.

Lensing approach to the Hubble constant

Cosmology The current expansion rate of the Universe is parametrized by the Hubble constant, H . Different methods of measuring H produce results that disagree with each other, which could be a sign of new physics or of systematic errors in the methods. Jee et al. have analyzed two gravitational lensing systems to determine their distances (see the Perspective by Davis). They use these as benchmarks for a measurement of H . The precision is not sufficient to resolve the debate but does bypass some of the systematic uncertainties. Observations of more lensing systems will be required to narrow down the value of H . Science , this issue p. [1134][1]; see also p. [1076][2] [1]: /lookup/doi/10.1126/science.aat7371 [2]: /lookup/doi/10.1126/science.aay1331

A measurement of the Hubble constant from angular diameter distances to two gravitational lenses

The local expansion rate of the Universe is parametrized by the Hubble constant, [Formula: see text], the ratio between recession velocity and distance. Different techniques lead to inconsistent estimates of [Formula: see text] Observations of Type Ia supernovae (SNe) can be used to measure [Formula: see text], but this requires an external calibrator to convert relative distances to absolute ones. We use the angular diameter distance to strong gravitational lenses as a suitable calibrator, which is only weakly sensitive to cosmological assumptions. We determine the angular diameter distances to two gravitational lenses, [Formula: see text] and [Formula: see text] megaparsec, at redshifts [Formula: see text] and 0.6304. Using these absolute distances to calibrate 740 previously measured relative distances to SNe, we measure the Hubble constant to be [Formula: see text] kilometers per second per megaparsec.

Same-sign WW scattering in the HEFT: discoverability vs. EFT validity

Vector boson scatterings are fundamental processes to shed light on the nature of the electroweak symmetry breaking mechanism. Deviations from the Standard Model predictions on the corresponding observables can be interpreted in terms of effective field theories, that however undergo consistency conditions. In this paper, the same-sign WW scattering is considered within the HEFT context and the correct usage of the effective field theory approach is discussed. Regions of the parameters space are identified where a signal of new physics could be measured at HL-LHC with a significance of more than 5σ and the effective field theory description is consistently adopted. These results are then translated into bounds on the ξ parameter in the composite Higgs scenario. The discussion on the agreement with previous literature and the comparison with the equivalent analysis in the SMEFT case are also included.

Signals of New Physics in B-Mesons Mixing Mass and Decay Width Differences

The measurement of $$ {B}_q^0-\overline{B_q^0} $$ (q = d, s) mixing mass difference and decay width differences is an important ingredient for searching physics beyond the standard model. In this paper, we investigate $$ {B}_q^0-\overline{B_q^0} $$ mixing mass and decay width differences in the Z′ model. It is found that these differences are enhanced relative to the standard model prediction and give signals for new physics. Depending upon the mass of Z′ boson, the Z′-mediated flavour-changing neutral current gives a contribution to mass and decay width differences in $$ {B}_q^0-\overline{B_q^0} $$ mixing.

Design and status of the Mu2e crystal calorimeter

The Mu2e experiment at Fermilab searches for the coherent neutrino-less muon to electron conversion in the Coulomb field of an aluminum nucleus. This charged-lepton flavor violating process is characterized by a distinctive signature of a mono-energetic electron (∼ 105 MeV/c) and its observation will be a clear signature of new physics beyond the Standard Model. The Mu2e goal is to improve by four orders of magnitude the search sensitivity with respect to the previous experiments. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter and an external veto for cosmic rays. The calorimeter plays an important role in providing excellent particle identification capabilities, a fast online trigger filter while aiding the track reconstruction capabilities. It consists of 1348 pure CsI crystals divided in two annular disks, each one readout by two large area Silicon Photomultipliers. A large scale prototype has been tested with an electron beam, demonstrating to largely satisfy the Mu2e requirements. At the moment of writing, the crystals and SiPMs production phase is halfway through the completion. An overview of the characterization tests is reported, together with a description of the final mechanical and electronical design.

Testing the cosmic distance-duality relation from future gravitational wave standard sirens

A validation of the cosmic distance-duality relation (CDDR) is crucial because any observational departure from it could be a signal of new physics. In this work, we explore the potentialities of luminosity distance data from the gravitational wave (GW) standard sirens of future Einstein Telescope (ET) to test the CDDR. The angular diameter distance data are used from the galaxy clusters samples and the baryon acoustic oscillation (BAO) measurements. The basic advantage of GW measurements substituting for the observations from the type Ia supernovae (SNIa) is that the luminosity distance from it is insensitive to the non-conservation of the number of photons. By simulating 550 and 1000 data points of future GW measurements in the low redshift range $0<z<1$, we show that the measurements of future GW events will be a powerful tool to test the CDDR.

B(s)→Ds0*(2317)P(V) decays in perturbative QCD approach

In this work, we use pQCD approach to calculate 20 $B_{(s)}\to D^*_{s0}(2317)P(V)$ two body decays by assuming $D^*_{s0}(2317)$ as a $\bar cs$ scalar meson, where $P(V)$ denotes a pseudoscalar (vector) meson. These $B_{(s)}$ decays can serve as an ideal platform to probe the valuable information on the inner structure of the charmed-strange meson $D^*_{s0}(2317)$, and to explore the dynamics of strong interactions and signals of new physics. These considered decays can be divided into two types: the CKM favored decays and the CKM suppressed decays. The former are induced by $b\to c$ transition, whose branching ratios are larger than $10^{-5}$. The branching fraction of the decay $\bar B^0_s\to D^{*+}_{s0}(2317)\rho^{-}$ is the largest and reaches about $1.8\times 10^{-3}$, while the branching ratios for the decay $\bar B^0_s\to D^{*+}_{s0}(2317)K^{*-}$ and other two pure annihilation decays $\bar B^0\to D^{*+}_{s0}(2317)K^-, D^{*+}_{s0}(2317)K^{*-}$ are only at $10^{-5}$ order. Our predictions are consistent well with the results given by the light cone sum rules approach. These decays are most likely to be measured at the running LHCb and the forthcoming SuperKEKB. The latter are induced by $b\to u$ transition, among of which the channel $\bar B^0\to D^{*-}(2317)\rho^+$ has the largest branching fraction, reaching up to $10^{-5}$ order. Again the pure annihilation decays $B^-\to D^{*-}_{s0}(2317)\phi, \bar B^0\to D^{*-}_{s0}(2317)K^+(K^{*+}), B^-\to D^{*-}_{s0}(2317)K^0(K^{*0})$, have the smallest branching ratios, which drop to as low as $10^{-10}\sim10^{-8}$.

Spotting hidden sectors with Higgs binoculars

We explore signals of new physics with two Higgs bosons and large missing transverse energy at the LHC. Such a signature is characteristic of models for dark matter or other secluded particles that couple to the standard model through an extended scalar sector. Our goal is to provide search strategies and an interpretation framework for this new signature that are applicable to a large class of models. To this end, we define simplified models of hidden sectors leading to two different event topologies: symmetric decay, i.e., pair-produced mediators decaying each into a Higgs plus invisible final state; and di-Higgs resonance, i.e., resonant Higgs-pair production recoiling against a pair of invisible particles. For both scenarios, we optimize the discovery potential by performing a multi-variate analysis of final states with four bottom quarks and missing energy, employing state-of-the-art machine learning algorithms for signal-background discrimination. We determine the parameter space that the LHC can test in both scenarios, thus facilitating an interpretation of our results in terms of complete models. Di-Higgs production with missing energy is competitive with other missing energy searches and thus provides a new opportunity to find hidden particles at the LHC.

Phenomenology of Minimal Composite Double Higgs Model

Higgs mechanism was a method to give mass into all particle in Standard Model. In 2012 research center CERN had detect Higgs particle with mass around 125 GeV. This data was not suitable with calculation, where based on Standard Model in high energy there are radiative correction to Higgs mass, so that Higgs have extremely heavy mass, we called these phenomena as hierarchy problem. Because of that reason there must be new theory based from Standard Model that can describe these phenomena, one of the theory is composite Higgs model where Higgs was a composite from Goldstone boson from symmetry breaking. Using Composite Higgs Model for minimal case and some modification to double Higgs. With this model we calculate Higgs mass correction and had same form of Higgs mass correction in Standard Model with extra term of , where ξ was one properties in composite Higgs and for ξ → 0 the model become back to Standard Model. Then we calculate the cut-off energy of the model with Renormalization Group Equation by Callan-Symanzik and give us cut-off energy at 106 GeV scale which far from GUT energy scale, so this model still acceptable. Otherwise This energy much higher than LHC energy, so we can not do direct observation then use Peskin-Takeuchi parameter which describe sign for new physics at high scale with calculation of vacuum polarization and the calculation results still fit with experiment data.

Guiding new physics searches with unsupervised learning

We propose a new scientific application of unsupervised learning techniques to boost our ability to search for new phenomena in data, by detecting discrepancies between two datasets. These could be, for example, a simulated standard-model background, and an observed dataset containing a potential hidden signal of New Physics. We build a statistical test upon a test statistic which measures deviations between two samples, using a Nearest Neighbors approach to estimate the local ratio of the density of points. The test is model-independent and non-parametric, requiring no knowledge of the shape of the underlying distributions, and it does not bin the data, thus retaining full information from the multidimensional feature space. As a proof-of-concept, we apply our method to synthetic Gaussian data, and to a simulated dark matter signal at the Large Hadron Collider. Even in the case where the background can not be simulated accurately enough to claim discovery, the technique is a powerful tool to identify regions of interest for further study.

Lepton flavour violation and neutrino masses

Neutrino oscillations provided the first evidence for the violation of flavour in the lepton sector, and established a clear need to consider extensions of the Standard Model. Many new phenomena can emerge from these New Physics (NP) constructions, among which processes violating lepton number and charged lepton flavour, all clear signals of New Physics. Following a short overview of the status of experimental searches, we comment on the prospects of several models of massive neutrinos, from minimal constructions to complete NP models, to the above mentioned observables.

A strategy for a general search for new phenomena using data-derived signal regions and its application within the ATLAS experiment

This paper describes a strategy for a general search used by the ATLAS Collaboration to find potential indications of new physics. Events are classified according to their final state into many event classes. For each event class an automated search algorithm tests whether the data are compatible with the Monte Carlo simulated expectation in several distributions sensitive to the effects of new physics. The significance of a deviation is quantified using pseudo-experiments. A data selection with a significant deviation defines a signal region for a dedicated follow-up analysis with an improved background expectation. The analysis of the data-derived signal regions on a new dataset allows a statistical interpretation without the large look-elsewhere effect. The sensitivity of the approach is discussed using Standard Model processes and benchmark signals of new physics. As an example, results are shown for 3.2 fb^{-1} of proton–proton collision data at a centre-of-mass energy of 13 text {TeV} collected with the ATLAS detector at the LHC in 2015, in which more than 700 event classes and more than 10^5 regions have been analysed. No significant deviations are found and consequently no data-derived signal regions for a follow-up analysis have been defined.

Cosmological Tests of Gravity with the Latest Observations

Abstract We perform observational tests of modified gravity on cosmological scales following model-dependent and model-independent approaches using the latest astronomical observations, including measurements of the local Hubble constant, cosmic microwave background, the baryonic acoustic oscillations and redshift space distortions derived from galaxy surveys including the Sloan Digital Sky Survey BOSS and eBOSS, as well as the weak lensing observations performed by the CFHTLenS team. Combining all these data sets, we find a deviation from the prediction of general relativity in both the effective Newton’s constant, μ(a, k), and in the gravitational slip, η(a, k). The deviation is at a 3.1σ level in the joint {μ(a, k), η(a, k)} space using a two-parameter phenomenological model for μ and η, and reaches a 3.7σ level if a general parameterization is used. This signal, which may be subject to unknown observational systematics, or a sign of new physics, is worth further investigating with forthcoming observations.

Direct and Indirect Probes for Composite Dark Matter

Dark matter candidates are one of the profound signatures of new physics, reflecting existence of new stable particles. If such particles are charged they can bind with ordinary electrons, forming anomalous isotopes. Severe constraints on the anomalous hydrogen exclude new stable single charged particles, but the case of stable double charged particles is not excluded so easily. Similar to ordinary baryonic matter dark matter candidates can be in the form of neutral dark atoms in which new stable or sufficiently long living double charged particles are bound by ordinary Coulomb interaction. In the most simple case only negative double charged particles are bound in O-helium (OHe) dark atoms with primordial helium. OHe hypothesis can provide the solution for puzzles of direct dark matter searches by specifics of OHe interaction in the matter of underground detectors. OHe interaction in the matter can lead to formation of various exotic forms of O-nuclearities. Provided that the mass of the double charged particle is around 1.25 TeV OHe hypothesis can explain the observed positron annihilation line excess in the galactic bulge by pair production in de-excitation of OHe atoms colliding in this region. In the model of Walking Technicolor generation of primordial excess of negatively charged techniparticles (over their antiparticles) can be related to the baryon asymmetry of the Universe, giving proper relationship of baryonic and non-baryonic matter densities. Such primordial excess may be accompanied by a subdominant excess of longliving positively double charged techniparticles, whose decay to same sign pair of leptons can explain the high energy cosmic positron anomaly, detected by PAMELA and AMS02. This explanation should be confronted with the cosmic gamma ray background measured by FERMI/LAT, what put upper limit on the mass of a decaying double charged particle. It makes search for stable double charged particles at the LHC a direct probe for composite dark matter hypothesis.

Critical Higgs inflation in a viable motivated model

An extension of the Standard Model with three right-handed neutrinos and a simple invisible axion model can account for all experimentally confirmed signals of new physics (neutrino oscillations, dark matter and baryon asymmetry) in addition to solving the strong CP problem, stabilizing the electroweak vacuum and satisfying all current observational bounds. We show that this model can also implement critical Higgs inflation, which corresponds to the frontier between stability and metastability of the electroweak vacuum. This leads to a value of the non-minimal coupling between the Higgs and the Ricci scalar that is much lower than the one usually quoted in Higgs inflation away from criticality. Then, an advantage is that the scale of perturbative unitarity breaking on flat spacetime can be very close to the Planck mass, where anyhow new physics is required. The higher dimensional operators are under control in this inflationary setup. The dependence of the cutoff on the Higgs background is also taken into account as appropriate when the Higgs is identified with the inflaton. Furthermore, critical Higgs inflation enjoys a robust inflationary attractor that makes it an appealing setup for the early universe. In the proposed model, unlike in the Standard Model, critical Higgs inflation can be realized without any tension with the observed quantities, such as the top mass and the strong coupling.

Lepton-flavor violation and two loop electroweak corrections to (g−2)μ in the B−L symmetric SSM

Charged lepton flavor violating processes are forbidden in the standard model (SM), hence the observation of charged lepton flavor transitions would represent a clear signal of new physics beyond the standard Model. In this work, we investigate some lepton flavor violating processes in the minimal supersymmetric extension of the SM with local $B-L$ gauge symmetry (B-LSSM). And including the corrections from some two loop diagrams to the anomalous dipole moments (MDM) of muon, we discuss the corresponding constraint on the relevant parameter space of the model. Considering the constraints from updated experimental data, the numerical results show that, new contributions in the B-LSSM enhance the MSSM predictions on the rates of $l_j-l_i$ transitions about one order of magnitude, and also enhance the MSSM prediction on the muon MDM. In addition, two loop electroweak corrections can make important contributions to the muon MDM in the B-LSSM.

D0-$ \bar {D}^0 $ mixing and CPV measurements at the B-factories

Measurements of D 0 - mixing and CP violation in D 0 decays are interesting as any difference with respect to the Standard Model prediction would be a signature of new physics. We report on recent searches and measurements of D 0 - mixing and CP violation in charm meson decays at BaBar and Belle experiments. In particular, the D 0 - mixing parameters in D 0 → π+ π − π0 are measured by the BaBar experiment for the first time with x = (1.5±1.2±0.6)% and y = (0.2±0.9±0.5)%. The first T-odd asymmetry measurement in D 0 → K 0 S π + π − π0 is performed at the Belle experiment with aCP = (−0.28 ±1.38+0.23 -0.76 )×10−3 , which is consistent with no CP violation. The measurements of CP asymmetry in D 0 → K S0 K0Swith ACP = (−2.9±5.2±2.2)% and D + → π+ π0 with ACP = (+2.31 ± 1.24 ± 0.23)% are also reported, which shows no CP violation.

Disentangling dark physics with cosmic microwave background experiments

We forecast constraints on dark matter (DM) scattering with baryons in the early Universe with upcoming and future cosmic microwave background (CMB) experiments, for DM particle masses down to 15 keV. In terms of the upper limit on the interaction cross section for a velocity-independent spin-independent elastic scattering, compared to current Planck results, we find a factor of $\sim$6 improvement with CMB-Stage 3, a factor of $\sim$26 with CMB-Stage 4, and a factor of $\sim$200 with a cosmic-variance limited experiment. Once the instrumental noise reaches the proximity of 1 $\mu$K-arcmin, the constraints are entirely driven by the lensing measurements. The constraints benefit from a wide survey, and show gradual improvement for instrumental noise levels from 10 $\mu$K-arcmin to 1 $\mu$K-arcmin and resolution from 5 arcmin to 1 arcmin. We further study degeneracies between DM interactions and various other signatures of new physics targeted by the CMB experiments. In the primary temperature and polarization only, we find moderate degeneracy between the effects of DM scattering, signals from massive neutrinos, and from the effective number of relativistic degrees of freedom. The degeneracy is almost entirely broken once the lensing convergence spectrum is included into the analyses. We discuss the implications of our findings in context of planned and upcoming CMB measurements and other cosmological probes of dark-sector and neutrino physics.

The ratio mathcal {R}(D) and the D-meson distribution amplitude

In this paper, we calculate the Brightarrow D transition form factors (TFFs) within the light-cone sum rules (LCSRs) and predict the ratio mathcal {R}(D). More accurate D-meson distribution amplitudes (DAs) are essential to get a more accurate theoretical prediction. We construct a new model for the twist-3 DAs phi ^p_{3;D} and phi ^sigma _{3;D} based on the QCD sum rules under the background field theory for their moments as we have done for constructing the leading-twist DA phi _{2;D}. As an application, we observe that the twist-3 contributions are sizable in whole q^2-region. Taking the twist-2 and twist-3 DAs into consideration, we obtain f^{Brightarrow D}_{+,0}(0) = 0.659^{+0.029}_{-0.032}. As a combination of the Lattice QCD and the QCD LCSR predictions on the TFFs f^{Brightarrow D}_{+,0}(q^2), we predict mathcal {R}(D) = 0.320^{+0.018}_{-0.021}, which is about 1.5sigma deviation from the HFAG average of the Belle and BABAR data. At present the data still have large errors, and we need further accurate measurements of the experiment to confirm whether there is a signal of new physics from the ratio mathcal {R}(D).