119209391
Four jets as a probe of O(100 GeV) physics beyond standard model at hadron colliders
O(100 GeV) physics beyond the standard model (BSM) could be overlooked provided that it is hidden in the untouched Higgs sector or jets. The top quark forward-backward asymmetry measurements and di-jet bump, which is observed in the associated production with charged lepton plus missing energy (supposed arising from W decay), may indicate the existence of a new color-octet axial-vector Z_C with a mass about 145 GeV. Here Z_C only decays into two jets. In this paper we investigated the possibility to discover Z_C pair via analyzing the four jets as the final states, which are heavily polluted by huge QCD background. Our simulation showed that, however, both Tevatron and LHC have the excellent chance to discover Z_C through analyzing the four jets events in the current accumulated data.
59418544
Discovering extra Higgs boson via pair production of the SM-like Higgs bosons
In the standard model (SM), pair production rate of Higgs boson at the Large Hadron Collider (LHC) is quite low. One usually think that it is extremely important for the measurement of triple Higgs coupling at the high luminosity LHC. In this paper, we propose to search for the extra Higgs boson (denoted as $S$) utilizing pair production of the SM-like Higgs boson ($H$) which was discovered in July, 2012.The pair production of $H$ can be huge due to the resonant production of heavy scalar $S$, namely $PP \rightarrow S \rightarrow HH$. The couplings of $H$ with weak gauge boson are similar to ones in the SM and it implies that the couplings between $S$ and gauge bosons are likely suppressed. Provided that $S$ is heavy enough, the decay into weak gauge bosons may not be the dominant modes. Instead $S$ can decay into a pair of $H$ and offer the promising channel to discover it. In this paper, we studied the 5 promising decay modes of $H$, i.e. $b\bar{b}$, $WW^*$, $ZZ^*$, $\gamma\gamma$ and $\tau^+\tau^-$, and simulated the signals and backgrounds for the 15 combination modes for $HH$ at the LHC with $\sqrt{s}= 14$ TeV and integrated luminosity $\mathcal{L}=1000fb^{-1}$. We found that with the help of suitable selection rules, very good signal to background ratio $S/B$ can be archived in many decay channels, for example $b\bar b+ (WW^*, ZZ^*, \gamma\gamma, \tau^+\tau^-)$, $WW^*+(WW^*, ZZ^*, \gamma\gamma, \tau^+\tau^-)$ and $\tau^+\tau^- +(\gamma\gamma, \tau^+\tau^-)$. For the detailed results please refer to Table \ref{tab:discovery} in the text. On the contrary, $b\bar b b\bar b$ mode is less important due to the huge QCD background. However if one has excellent control on light jet mis-tagging, the $b\bar b b\bar b$ mode can be promising to discover the extra Higgs boson due to its the largest branching ratio compared to other modes.
116998495
Probing lepton flavor violation signal via e+ e- (gamma gamma) ---> l(i) anti-l(j) in the littlest Higgs model with T-parity at the ILC
In the littlest Higgs model with T-parity, the new interactions between the mirror leptons and the Standard Model leptons can induce some lepton flavor violation (LFV) processes at loop level. We study the possibility of the ILC to probe the LFV production processes $e^+e^-(\gamma\gamma)\rightarrow l_{i}\bar{l}_{j}$. Our results show that the rates of $\gamma\gamma\rightarrow l_{i}\bar{l}_{j}$ can reach 1 fb in optimal cases after reasonable kinematical cuts, which implies that these processes may be observed at the ILC.
55046954
Berkeley Supernova Ia Program - I. Observations, data reduction and spectroscopic sample of 582 low-redshift Type Ia supernovae
In this first paper in a series, we present 1298 low-redshift (z ≲ 0.2) optical spectra of 582 Type Ia supernovae (SNe Ia) observed from 1989 to 2008 as part of the Berkeley Supernova Ia Program (BSNIP). 584 spectra of 199 SNe Ia have well-calibrated light curves with measured distance moduli, and many of the spectra have been corrected for host-galaxy contamination. Most of the data were obtained using the Kast double spectrograph mounted on the Shane 3 m telescope at Lick Observatory and have a typical wavelength range of 3300–10 400 A, roughly twice as wide as spectra from most previously published data sets. We present our observing and reduction procedures, and we describe the resulting SN Database, which will be an online, public, searchable data base containing all of our fully reduced spectra and companion photometry. In addition, we discuss our spectral classification scheme (using the SuperNova IDentification code, snid; Blondin & Tonry), utilizing our newly constructed set of snid spectral templates. These templates allow us to accurately classify our entire data set, and by doing so we are able to reclassify a handful of objects as bona fide SNe Ia and a few other objects as members of some of the peculiar SN Ia subtypes. In fact, our data set includes spectra of nearly 90 spectroscopically peculiar SNe Ia. We also present spectroscopic host-galaxy redshifts of some SNe Ia where these values were previously unknown. The sheer size of the BSNIP data set and the consistency of our observation and reduction methods make this sample unique among all other published SN Ia data sets and complementary in many ways to the large, low-redshift SN Ia spectra presented by Matheson et al. and Blondin et al. In other BSNIP papers in this series, we use these data to examine the relationships between spectroscopic characteristics and various observables such as photometric and host-galaxy properties.
124732549
Beam emittance investigation in high brightness injector using different driver laser profiles
Beam emittance plays an important role in any accelerator, and it is a main parameter to judge the performance of an accelerator. Emittance optimization is an indispensable part in conditioning and operation of the facility. For a laser-driven high brightness injector, different time structure of the laser pulse has different effects on transverse emittance. In order to compare Gaussian and flat-top laser pulse, systematic simulations of 500 pC have been done. From the simulation results, one can see that flat-top pulse laser will yield smaller minimal transverse beam size and transverse beam emittance than Gaussian pulse laser.
76655214
Hadron production in p+p, p+Pb, and Pb+Pb collisions with the HIJING 2.0 model at energies available at the CERN Large Hadron Collider
The Heavy-Ion Jet Interaction Generator (hijing) Monte Carlo model is updated with the latest parton distributions functions and a new set of the parameters in the two-component minijet model that controls the total p+p cross section and the central pseudorapity density. We study hadron spectra and multiplicity distributions using the hijing2.0 model and compare to recent experimental data from p+p collisions at the Large Hadron Collider (LHC) energies. We also give predictions of hadron production in p+p, p+Pb, and Pb+Pb collisions at the full LHC energy.
122096987
ASSOCIATED PRODUCTION OF SINGLE HEAVY T-QUARK IN THE LEFT–RIGHT TWIN HIGGS MODEL AT THE LHC
The heavy T-quark is one of the most crucial ingredients in the left–right twin Higgs model, which is introduced to cancel the largest contribution of the Standard Model top quark to the Higgs boson mass at one-loop level. In this paper, we study the relevant single heavy T-quark production processes, the 2 → 2 partonic processes of qb → q'T and , the 2 → 3 partonic processes of and at the CERN LHC. Our numerical results show that the 2 → 3 process can be quite important, as its cross-section is about 60% of that for the 2 → 2 process at the LHC. We also show the pT distribution and the rapidity distributions for out-going particles. For the 2 → 3 process, the production rate of the final state can be larger than 100 fb with reasonable values of the free parameters. The possible signatures of the heavy T-quark might be detected via the process at the LHC.