Mass Difference Δm Research Articles

Improved limits on n→n′ transformation from the Spallation Neutron Source

Conversions between neutrons n and dark matter candidate sterile neutrons n′ have been proposed as a mechanism for baryon number B violation. In the case that there is a small mass difference Δm between the n and the n′ states, oscillations can be induced by compensating for Δm with a magnetic field. A search for such neutron oscillations was performed at the Spallation Neutron Source by looking for anomalous neutron transmission through a strongly absorbing cadmium wafer inside of a 6.6 T magnet. The approach described here saw no regenerated neutrons above background, which provides an improved limit for neutron–sterile neutron transformations for a range of Δm between 0.1 and 1000 neV. Published by the American Physical Society 2024

Search for charged excited states of dark matter with KamLAND-Zen

Particle dark matter could belong to a multiplet that includes an electrically charged state. WIMP dark matter (χ0) accompanied by a negatively charged excited state (χ−) with a small mass difference (e.g. < 20 MeV) can form a bound-state with a nucleus such as xenon. This bound-state formation is rare and the released energy is O(1−10) MeV depending on the nucleus, making large liquid scintillator detectors suitable for detection. We searched for bound-state formation events with xenon in two experimental phases of the KamLAND-Zen experiment, a xenon-doped liquid scintillator detector. No statistically significant events were observed. For a benchmark parameter set of WIMP mass mχ0=1 TeV and mass difference Δm=17 MeV, we set the most stringent upper limits on the recombination cross section times velocity 〈σv〉 and the decay-width of χ− to 9.2×10−30cm3/s and 8.7×10−14 GeV, respectively at 90% confidence level.

B 0— B¯0 mixing in the U(1) X SSM

U(1) X SSM is a non-universal Abelian extension of the Minimal Supersymmetric Standard Model and its local gauge group is extended to SU(3) C × SU(2) L × U(1) Y × U(1) X . Based on the latest data of neutral meson mixing and experimental limitations, we investigate the process of B0−B0¯ mixing in U(1) X SSM. Using the effective Hamiltonian method, the Wilson coefficients and mass difference Δm B are derived. The abundant numerical results verify that vS,MD2,λC,μ,M2,tanβ,gYX,M1 and λ H are sensitive parameters to the process of B0−B0¯ mixing. With further measurement in the experiment, the parameter space of the U(1) X SSM will be further constrained during the mixing process of B0−B0¯ .

The role of U(1) A symmetry breaking in the QCD corrections to the pion mass difference

The charged and neutral pion mass difference can be attributed to both the quantum electrodynamics and QCD contributions. The current quark mass difference (Δm) is the source of the QCD contribution. Here, in a two-flavour non-local Nambu–Jona-Lasinio model, we try to estimate the QCD contribution. Interestingly, we find that the strength of the symmetry-breaking parameter c plays a crucial role in obtaining the pion mass difference while intertwined with the current quark mass difference. To obtain the QCD contribution for the pion mass difference, we scan the parameter space in {Δm, c}, and by comparing this with the existing results, we constrained the parameter space. Further, using a fitted value of c, we determine the allowed range for the Δm in the model. The model estimated Δm ranges enable us to extract the chiral perturbation theory low energy constant, l 7 and verify the dependence of the pion mass difference on Δm. We also find out its dependence on c—it increases with the decreasing value of c, i.e. toward an axial anomaly restored phase.

Synergistic interaction for catalytic co-pyrolysis of municipal paper and polyethylene terephthalate wastes coupling with deep learning methodology

Municipal papers and polyethylene terephthalate (PET) wastes are primary constituents of municipal solid waste (MSW) which necessitates effective disposal. Co-pyrolysis is an efficient transformation technology for the production of valuable gas and liquid fuels. Therefore, co-pyrolysis characteristics, kinetics, gas and liquid products of cellulose and PET mixtures were investigated in a two-stage reactor by multiple characterizations coupling with deep learning approach. The results indicated that there exhibited positive interaction for cellulose and PET co-pyrolysis in terms of mass difference (δm) and mass loss rate difference (δr) between experimental and calculated values. The thermal decomposition process and synergistic effects (δm and δr) were accurately predicted by deep learning approaches (R2 =0.9823–0.9993) using temperature, catalyst, mixing ratio and heating rate variables. Feature importance revealed that the temperature, catalyst, heating rate and mixing ratio were in the descending order to affect the remaining mass from TG curves. And the temperature played a predominant role in synergistic effects. The Flynn-Wall-Ozawa (FWO) method was more suitable for fitting the pyrolysis process to obtain activation energy (Ea) with higher R2 (0.94714–0.99640) compared with Kissinger-Akahira-Sunose (KAS) method. When the mixing ratio of cellulose and PET was 1:1, the Ea was significantly reduced to 80.73 KJ/mol, and further reduced to 73.04 KJ/mol by introducing the catalyst, as compared to Ea of individual cellulose (178.95 KJ/mol) and PET (198.34 KJ/mol). Co-pyrolysis of cellulose and PET led to a reduction of carbohydrates, furans, alcohols, ketones, and phenols, while the content of acids was remarkably increased which was consistent with the observation in FTIR that the absorption peak of C＝O became sharp and strong. The introduction of ZSM-11 resulted in an increase in aromatics and a decrease in acids content owing to aromatization and deoxygenation. This work is expected to offer beneficial guidance for the efficient disposal of MSW and the application of deep learning methods.

Resolution and Resolving Power in Mass Spectrometry.

The term resolution is one of the most important in mass spectrometry because it describes the ability to separate peaks in mass spectra. The term resolving power is often used to describe the ability of a mass spectrometer to resolve adjacent peaks in a mass spectrum and is often used interchangeably with resolution. The separation of peaks for singly charged ions can be expressed as a mass difference Δm and the ratio m/Δm is often given as a quantitative measure of the ability of a mass spectrometer to separate ions. Over the past 50 years, several definitions of mass resolution and mass resolving power have been recommended both by the International Union for Pure and Applied Chemistry and the American Society for Mass Spectrometry that define both resolution or resolving power as m/Δm which has led to confusion about the proper use of these terms. The goal of this work is to investigate the origins and use as well as prior and current definitions of resolution and resolving power and make recommendations for the definition of these terms.

Mass Difference Matching Unfolds Hidden Molecular Structures of Dissolved Organic Matter.

Ultrahigh-resolution Fourier transform mass spectrometry (FTMS) has revealed unprecedented details of natural complex mixtures such as dissolved organic matter (DOM) on a molecular formula level, but we lack approaches to access the underlying structural complexity. We here explore the hypothesis that every DOM precursor ion is potentially linked with all emerging product ions in FTMS2 experiments. The resulting mass difference (Δm) matrix is deconvoluted to isolate individual precursor ion Δm profiles and matched with structural information, which was derived from 42 Δm features from 14 in-house reference compounds and a global set of 11 477 Δm features with assigned structure specificities, using a dataset of ∼18 000 unique structures. We show that Δm matching is highly sensitive in predicting potential precursor ion identities in terms of molecular and structural composition. Additionally, the approach identified unresolved precursor ions and missing elements in molecular formula annotation (P, Cl, F). Our study provides first results on how Δm matching refines structural annotations in van Krevelen space but simultaneously demonstrates the wide overlap between potential structural classes. We show that this effect is likely driven by chemodiversity and offers an explanation for the observed ubiquitous presence of molecules in the center of the van Krevelen space. Our promising first results suggest that Δm matching can both unfold the structural information encrypted in DOM and assess the quality of FTMS-derived molecular formulas of complex mixtures in general.

Precise determination of Ar, Kr and Xe isotopic fractionation due to diffusion and dissolution in fresh water

Dissolved noble gases are ideal conservative tracers of physical processes in the Earth system due to their chemical and biological inertness. Although bulk concentrations of dissolved Ar, Kr, and Xe are commonly measured to constrain physical models of atmosphere, ocean, and terrestrial hydrosphere processes, stable isotope ratios of these gases (e.g. 136Xe/129Xe) are seldom used because of low signal-to-noise ratios. Here we present the first results from a new method of dissolved gas sampling, extraction and analysis that permits measurement of stable Ar, Kr, and Xe isotope ratios at or below ∼5 per meg amu−1 precision (1σ), two orders-of-magnitude below conventional Kr and Xe isotopic measurements. This gain in precision was achieved by quantitative extraction and subsequent purification of dissolved noble gases from 2-L water samples via helium sparging and viscous dual-inlet isotope ratio mass spectrometry. We have determined the solubility fractionation factors (αsol) for stable Ar, Kr, and Xe isotope ratios between ∼2 and 20°C via laboratory equilibration experiments. We have also conducted temperature-controlled air-water gas exchange experiments to estimate the kinetic fractionation factors (αkin) of these isotope ratios. We find that both αsol and αkin, normalized by isotopic mass difference (Δm), decrease in magnitude with atomic number but are proportional to Δm for isotope ratios of the same element. With the new ability for high precision isotopic measurements, we suggest that dissolved Kr and Xe isotope ratios in groundwater represent a promising, novel geochemical tool with important applications for groundwater modeling, water resource management, and paleoclimate.

The string origin of SUSY flavor violation

We argue that in large classes of string compactifications with a MSSM-like structure substantial flavor violating SUSY-breaking soft terms are generically induced. We specify to the case of flavor dependent soft-terms in type IIB/F-theory SU(5) unified models, although our results can be easily extended to other settings. The Standard Model (SM) degrees of freedom reside in a local system of 7-branes wrapping a 4-fold S in the extra dimensions. It is known that in the presence of closed string 3-form fluxes SUSY-breaking terms are typically generated. We explore the generation dependence of these soft terms and find that non-universalities arise whenever the flux varies over the 4-fold S. These non-universalities are parametrically suppressed by (M GUT /M Pl)1/3. They also arise in the case of varying open string fluxes, in this case parametrically suppressed by $ \alpha_{\mathrm{GUT}}^{{{1 \left/ {2} \right.}}} $ . For a standard unification scheme with M GUT ≃ 1016 GeV and α GUT ≃ 1/24 these suppressions are very mild. Although limits from the kaon mass difference Δm K are easily obeyed for squark masses above the present LHC limits, constraints from the CP-violation parameter ϵ K imply squark masses in the multi-TeV region. The constraints from BR(μ → eγ) turn out to be the strongest ones, with slepton masses of order ~ 10 TeV or heavier required to obey the experimental limits. These sfermion masses are consistent with the observed large value m H ≃ 126 GeV of the Higgs mass. We discuss under what conditions such strong limits may be relaxed allowing for SUSY particle production at LHC.

Relative quantitation of glycans using stable isotopic labels 1-(d0/d5) phenyl-3-methyl-5-pyrazolone by mass spectrometry

A deuterium reagent, 1-(d5) phenyl-3-methyl-5-pyrazolone (d5-PMP), has been synthesized and used for relative quantitative analysis of oligosaccharides by mass spectrometry (MS) using d0/d5-PMP stable isotopic labeling. Previously reported permethylation-based isotopic labels generate variable mass differences, and reductive amination-based isotopic labels cause a loss of some acid-labile groups in carbohydrates. In contrast, d0/d5-PMP stable isotopic labeling is performed at the reducing end of glycans under basic conditions without desialylation, and the mass difference (Δm=10Da) between the heavy form (d5-PMP derivative) and light form (d0-PMP derivative) of each glycan is invariable. When the two derivative forms of a glycan are mixed in equimolar amounts, a pair of peaks with a 10-Da mass differences is observed in the MS profile. The difference at relative intensity between the d0- and d5-PMP derivatives reflects the difference in quantity of glycans in two samples, making it possible to carry out both qualitative and relative quantitative analyses of glycans in glycomic studies. Application of this method on DP2 to DP6 maltodextrin oligosaccharides and N-linked glycans released from ribonuclease B and bovine fetuin demonstrates a 10-fold relative quantitative dynamic range, a satisfying reproducibility (coefficient of variation [CV]⩽8.34%), and good accuracy (relative error [RE]⩽5.1%) of the method. The suggested technique has been successfully applied for comparative quantitative analysis of free oligosaccharides in human and bovine milk.

10.1007/s11450-008-2018-3

Mixing in the systems of neutral K 0 and B 0 mesons is considered within the minimal supersymmetric standard model (MSSM) containing a type-II Yukawa sector and featuring an explicitCP violation in the Higgs potential. In the case of a strong mixing of CP-even and CP-odd states, the model admits the presence of a light charged Higgs boson. Basic mixing parameters are calculated. These include the mass difference Δm LS between neutral kaons and the parameter ε, which characterizes the amount of an indirect CP violation (that is, that which arises owing to an ultraweak mixing of CP-invariant and CP-noninvariant components). In the limit of the low-energy one-loop approximation, it is shown that, for the K 0 mesons, the contribution of nonstandard-physics effects to the mass splitting of the neutral kaons and an indirect CP violation are very small and are weakly dependent on the mass of the charged Higgs boson. Under certain conditions, the nonstandard contributions for the B 0-\( \bar B_d^0 \) and B 0-\( \bar B_s^0 \) systems may become somewhat more substantial, which constrains the MSSM parameter space.

Two Higgs bi-doublet left-right model with spontaneous P and CP violation

A left-right symmetric model with two Higgs bi-doublet is shown to be a consistent model for both spontaneous P and CP violation. The flavor changing neutral currents can be suppressed by the mechanism of approximate global U(1) family symmetry. The constraints from neural K meson mass difference Δm K are calculated and it is demonstrated that a right-handed gauge boson W 2 contribution in box-diagrams with mass well below 1 TeV is allowed due to a cancelation caused by a light-charged Higgs boson with a mass range of 150–300 GeV. The W 2 contribution to ε K can be suppressed from an appropriate choice of additional CP phases appearing in the right-handed Cabbibo-Kobayashi-Maskawa matrix. The model is also found to be fully consistent with B 0 mass difference Δm B and the mixing induced CP violation sin2β J/ Ψ, which is usually difficult for the model with only one Higgs bi-doublet. The new physics beyond the standard model can be directly searched at the colliders LHC and ILC.

Properties ofL=1B1andB2*Mesons

This Letter presents the first strong evidence for the resolution of the excited B mesons B1 and B2* as two separate states in fully reconstructed decays to B+(*)π−. The mass of B1 is measured to be 5720.6±2.4±1.4 MeV/c2 and the mass difference ΔM between B2* and B1 is 26.2±3.1±0.9 MeV/c2, giving the mass of the B2* as 5746.8±2.4±1.7 MeV/c2. The production rate for B1 and B2* mesons is determined to be a fraction (13.9±1.9±3.2)% of the production rate of the B+ meson.Received 23 May 2007DOI:https://doi.org/10.1103/PhysRevLett.99.172001©2007 American Physical Society

Indirect measurements of the τ˜–χ˜10 mass difference and Mg˜ in the co-annihilation region of mSUGRA models at the LHC

Abstract We study the prospects for the measurement of the τ ˜ – χ ˜ 1 0 mass difference (ΔM) and the g ˜ mass ( M g ˜ ) in the supersymmetric co-annihilation region of mSUGRA at the LHC using tau leptons. Recent WMAP measurements of the amount of cold dark matter and previous accelerator experiments favor the co-annihilation region of mSUGRA, characterized by a small ΔM (5–15 GeV). Focusing on taus from χ ˜ 2 0 → τ τ ˜ → τ τ χ ˜ 1 0 decays in g ˜ and q ˜ production, we consider inclusive 3 τ + jet + E T production, with two τ's above a high E T threshold and a third τ above a lower threshold. Two observables, the number of opposite-signed τ pairs minus the number of like-signed τ pairs, and the peak of the di-tau invariant mass distribution, allow for the simultaneous determination of ΔM and M g ˜ for Δ M ≳ 6 GeV . For example, for Δ M = 9 GeV and M g ˜ = 850 GeV with 30 fb −1 of data, we can measure ΔM to 15% and M g ˜ to 6%.

Detection of SUSY in the stau–neutralino coannihilation region at the LHC

Abstract We study the feasibility of detecting the stau neutralino ( τ ˜ 1 – χ ˜ 1 0 ) coannihilation region at the LHC using tau (τ) leptons. The signal is characterized by multiple low energy τ leptons from χ ˜ 2 0 → τ τ ˜ 1 → τ τ χ ˜ 1 0 decays, where the τ ˜ 1 and χ ˜ 1 0 mass difference (ΔM) is constrained to be 5–15 GeV by current experimental bounds including the bound on the amount of neutralino cold dark matter. Within the framework of minimal supergravity models, we show that if hadronically decaying τ's can be identified with 50% efficiency for visible p T > 20 GeV the observation of such signals is possible in the final state of two τ leptons plus large missing energy and two jets. With a gluino mass of 830 GeV the signal can be observed with as few as 3 – 10 fb −1 of data (depending on the size of ΔM). Using a mass measurement of the τ pairs with 10 fb −1 we can determine ΔM with a statistical uncertainty of 12% for Δ M = 10 GeV and an additional systematic uncertainty of 14% if the gluino mass has an uncertainty of 5%.

SEARCH FOR $D^0-\overline{D}^0$ MIXING USING SEMILEPTONIC DECAYS

Based on an 87-fb-1 dataset collected by the Babar detector at the PEP-II asymmetric-energy B-Factory, a search for [Formula: see text] mixing has been made using the semileptonic decay modes D*+ → π+D0, D0 → Kev (+c.c.) . The use of these modes allows unambiguous flavor tagging and a combined fit of the D0 decay time and D*+-D0 mass difference (ΔM) distributions. The high-statistics sample of unmixed semileptonic D0 decays is used to model the ΔM distribution and time-dependence of mixed events directly from the data. Neural networks are used to select events and reconstruct the D0. A result consistent with no charm mixing has been obtained, R mix = 0.0023 ± 0.0012 ± 0.0004. This corresponds to an upper limit of R mix &lt; 0.0042 (90% CL).

B0d, s– [formula omitted] mass-differences from QCD spectral sum rules

We present the first QCD spectral sum rules analysis of the SU(3) breaking parameter ξ and an improved estimate of the renormalization group invariant (RGI) bag constant B B q both entering into the B 0 d, s – B 0 d,s mass-differences. The averages of the results from the Laplace and moment sum rules to order α s are f B B B ≃(247±59) MeV and ξ≡ f B s B B s f B B B ≃(1.18±0.03) , in units where f π =130.7 MeV. Combined with the experimental data on the mass-differences ΔM d, s , one obtains the constraint on the CKM weak mixing angle | V ts / V td | 2⩾20.0(1.1). Alternatively, using the weak mixing angle from the analysis of the unitarity triangle and the data on ΔM d , one predicts ΔM s =18.6(2.2) ps −1 in agreement with the present experimental lower bound and within the reach of Tevatron 2.

ΔMs/ ΔMd, sin2 β and the angle γ in the presence of new ΔF=2 operators

We present formulae for the mass differences ΔM d and ΔM s in the B ̄ d,s 0 – B d, s 0 systems and for the CP violation parameter ε which are valid in minimal flavour violation models giving rise to new four-fermion ΔF=2 operators. Short distance contributions to ΔM s , ΔM d and ε are parameterized by three real functions F s tt , F d tt and F ε tt , respectively ( F s tt = F d tt = F ε tt holds only if the Standard Model ( V− A)⊗( V− A) operators dominate). We present simple strategies involving the ratio ΔM s / ΔM d , sin2 β and γ that allow to search for the effects of the new operators. We point out that their sizable contributions to the ratio ΔM s / ΔM d would in principle allow γ to be larger than 90°. Constraints on the functions F i tt imposed by the present (and future) experimental data are also discussed. As an example we show that for large tan β ̄ ≡v 2/v 1 and H + not too heavy, F s tt in the MSSM with heavy sparticles can be substantially smaller than in the SM due the charged Higgs box contributions and in particular due to the growing like tan 4 β ̄ contribution of the double penguin diagrams involving neutral Higgs boson exchanges. As a result the bounds on the function F s tt can be violated which allows to exclude large mixing of stops. In this scenario the range of sin2 β following from ε and ΔM d is identical to the SM ones (0.5<sin2 β<0.8). On the other hand γ following from ΔM s / ΔM d is lower.

Type-II supernovae and neutrino magnetic moments

The present solar and atmospheric neutrino data together with the LSND results and the presence of hot dark matter (HDM) suggest the existence of a sterile neutrino at the eV scale. We have reanalysed the effect of resonant sterile neutrino conversions induced by neutrino magnetic moments in a type-II supernova. We analyse the implications of ν e - ν s and ν e - ν s ( ν s denotes sterile neutrino) conversions for the supernova shock reheating, the detected ν e signal from SN1987A and the r-process nucleosynthesis hypothesis. Using reasonable magnetic field profiles we determine the sensitivity of these three arguments to the relevant neutrino parameters, i.e., the value of the transition magnetic moment and the ν e - ν s mass difference Δm 2 ≡ Δm LSND/HDM 2

Status of K2K (KEK to Kamioka long baseline neutrino oscillation experiment)

The purpose of K2K (KEK-PS E362) experiment [1] is to draw a definite conclusion on the neutrino oscillations with squared mass differences Δm 2 below 10 −1 eV 2. The experiment uses a well-defined muon neutrino ( v μ ) beam produced at the KEK-PS and two detectors, including the existing Super-Kamiokande detector. The experiment will be sensitive to the ν μ → ν e and ν μ → ν τ oscillations, Δm 2 ≥ 3 × 10 −3 eV 2 with more than the 99% confidence level for large mixing angle. The experimental methods, status, and schedule are described.