$\rm{K}^{*}(\rm{892})^{0}$ and $\phi(1020)$ production at midrapidity in pp collisions at $\sqrt{s}$ = 8 TeV

The production of $\rm{K}^{*}(\rm{892})^{0}$ and $\phi(1020)$ in pp collisions at $\sqrt{s}$ = 8 TeV were measured using Run 1 data collected by the ALICE collaboration at the LHC. The $p_{\rm{T}}$-differential yields d$^{\rm 2}N$/d$y$d$p_{\rm{T}}$ in the range 0 $<$ $p_{\rm{T}}$ $<$ 20 GeV/$c$ for $\rm{K}^{*0}$ and 0.4 $<$ $p_{\rm{T}}$ $<$ 16 GeV/$c$ for $\phi$ have been measured at midrapidity $|y|$ $<$ 0.5. Moreover, improved measurements of the $\rm{K}^{*}(892)^{0}$ and $\phi(1020)$ at $\sqrt{s}$ = 7 TeV are presented. The collision energy dependence of $p_{\rm{T}}$ distributions, $p_{\rm{T}}$-integrated yields and particle ratios in inelastic pp collisions are examined. The results are also compared with different collision systems. The values of the particle ratios are measured to be similar to those found at other LHC energies. In pp collisions a hardening of the particle spectra is observed with increasing energy, but at the same time it is also observed that the relative particle abundances are independent of the collision energy. The $p_{\rm{T}}$-differential yields of $\rm{K}^{*0}$ and $\phi$ in pp collisions at $\sqrt{s}$ = 8 TeV are compared with the expectations of different Monte Carlo event generators.


Introduction
The study of resonances plays an important role in understanding particle production mechanisms.Particle production at LHC energies has both soft and hard-scattering origins.The hard scatterings are perturbative processes and are responsible for production of high-p T particles, whereas the bulk of the particles are produced due to soft interactions, which are non-perturbative in nature.High-p T particles originate from fragmentation of jets and their yield can be calculated by folding the perturbative Quantum Chromodynamics (pQCD) calculations for elementary parton-parton scatterings with universal fragmentation functions determined from experimental data [1][2][3].The production yield of low-p T particles can not be estimated from the first principles of QCD, hence predictions require phenomenological models in the non-perturbative regime.In this paper, we discuss K * 0 (892) and φ (1020) production in pp collisions at √ s = 8 TeV.The φ (1020) meson is a vector meson consisting of strange quarks (ss).The production of ss pairs was found to be significantly suppressed, compared to uu and dd pairs in pp collisions due to the larger mass of the strange quark [4,5].The K * 0 (892) is a vector meson with a similar mass to the φ (1020), but differs in strangeness content by one unit, which may help in understanding the strangeness production dynamics.Measurements of particle production in inelastic pp collisions provide input to tune the QCD inspired Monte Carlo (MC) event generators such as EPOS [6], PYTHIA [7] and PHO-JET [8,9].Furthermore, the measurements in inelastic pp collisions at √ s = 8 TeV reported in this paper serve as reference data to study nuclear effects in proton−lead (p-Pb) and lead−lead (Pb-Pb) collisions.
In this article, the p T -differential and p T -integrated yields and the mean transverse momenta of K * 0 (892) and φ (1020) at midrapidity in pp collisions at √ s = 8 TeV are presented.The energy dependence of the p T distributions and particle ratios to the charged pions and kaons in pp collisions is examined and discussed.The yields of pions and kaons measured previously by ALICE [10,11] at √ s = 0.9 and 7 TeV are used to obtain the yields in pp collisions at √ s = 8 TeV.Moreover, updated measurements of the K * 0 (892) and φ (1020) at √ s = 7 TeV are presented; our first measurements for that collision system were published in Ref. [12].These results include an extension of the K * 0 (892) measurement to high p T and an improved re-analysis of the φ (1020).This measurement has updated track-selection cuts, which are identical to those described for the measurements at √ s = 8 TeV, has an improved estimate of the systematic uncertainties, and extends to greater values of p T .Throughout this paper, the results for K * (892) 0 and K * (892) 0 are averaged and denoted by the symbol K * 0 , while φ (1020) is denoted by φ unless specified otherwise.
This article is organized as follows.The experimental setup is briefly explained in Sec. 2 and the analysis procedure is given in Sec. 3. The results and discussions are presented in Sec. 4 followed by the conclusions in Sec. 5.

Experimental setup
The ALICE detector can be used to reconstruct and identify particles over a wide momentum range, thanks to the low material budget, the moderate magnetic field and the presence of detectors with excellent particle identification (PID) techniques.The comprehensive description of the detector and its performance during the LHC Run 1 are reported in Refs.[13,14].
The detectors used for this analysis are described in the following.V0 detectors are two plastic scintillator arrays used for the triggering and event characterization.They are placed along the beam direction at 3.3 m (V0A) and −0.9 m (V0C) on either side of the interaction point with a pseudorapidity coverage of 2.8 < η < 5.1 and −3.7 < η < −1.7, respectively.The Inner Tracking System (ITS), which is located between 3.9 cm and 43 cm radial distance from the beam axis, is made up of six layers of cylindrical silicon detectors (2 layers of silicon pixels, 2 layers of silicon drift and 2 layers of double-side silicon strips).As it provides high-resolution space points close to the interaction point, the momentum and angular resolution of the tracks reconstructed in the Time Projection Chamber (TPC) is improved.√ s = 8 TeV ALICE Collaboration The TPC is the main tracking device covering full azimuthal acceptance and the pseudorapidity range −0.9 < η < 0.9.It is a 92 m 3 cylindrical drift chamber filled with an active gas.It is divided in two parts by a central cathode and the end plates consist of multi-wire proportional chambers.The TPC is also used for particle identification via the measurement of the specific ionization energy loss (dE/dx) via ionization in the gas.The Time of Flight (TOF) detector consists of large multigap resistive plate chambers.It has pseudorapidity coverage −0.9 < η < 0.9, full azimuthal acceptance and a time resolution of < 50 ps.The TOF is used for the particle identification at intermediate momenta.The particle identification techniques based on the TPC and TOF signals are presented in detail in the next section.

Data analysis
The measurements of K * 0 and φ meson production in pp collisions at √ s = 8 TeV were performed during Run 1 data taking with the ALICE detector in 2012 using a minimum bias trigger as discussed in Sec.3.1.A total of around 45M events were analysed for both √ s = 7 and 8 TeV and the corresponding integrated luminosities are 0.72 nb −1 and 0.81 nb −1 , respectively.The K * 0 and φ resonances are reconstructed via their hadronic decay channels with large branching ratios (BR): K * 0 → π ± K ∓ with BR = 66.6% and φ → K + K − with the recent updated BR = 49.2%[15].When comparing the new φ results to older ones, the old results are scaled by the ratio 0.489/0.492[15,16] to account for the new branching ratio value.

Event and track selection
For pp collisions at √ s = 8 TeV, the events were selected with a minimum bias trigger based on a coincidence signal in V0A and V0C.For pp collisions at √ s = 7 TeV, the trigger condition is same as in [12].The ITS and TPC are used for tracking and reconstruction of charged particles and of the primary vertex.Events having the primary vertex coordinate along the beam axis within 10 cm from the nominal interaction point are selected.Pile-up events are rejected if more than one vertex is found with the Silicon Pixel Detector (SPD).A primary track traversing the TPC induces signals on a maximum of 159 tangential pad-rows, each corresponding to one cluster used in track reconstruction.For this analysis high quality charged tracks are used, to select pion and kaon candidates coming from the decays of K * 0 and φ .Tracks are required to have at least 70 TPC clusters and a χ 2 per track point (χ 2 /N clusters ) of the track fit in the TPC less than 4.Moreover, tracks must be associated with at least one cluster in the SPD.To ensure a uniform acceptance by avoiding the edges of the TPC, tracks are selected within |η| < 0.8.In order to reduce contamination from secondary particles coming from weak decays, cuts on the distance of closest approach to the primary vertex in the transverse plane (DCA xy ) and longitudinal direction (DCA z ) are applied.The value of DCA xy is required to be less than 7 times its resolution: DCA xy (p T ) < (0.0105 + 0.035p −1.1 T ) cm (p T in GeV/c) and DCA z is required to be less than 2 cm.To improve the global resolution, the p T of each track is choosen to be greater than 0.15 GeV/c.In the TPC, particles are identified by measuring the dE/dx in the TPC gas, whereas in the TOF it is done by measuring the time of flight.The particles in the TPC are selected using a cut on the difference of the mean value of the dE/dx to the expected dE/dx value for a given species divided by the resolution σ TPC .This cut is expressed in units of the estimated σ TPC .As described below, this is optimized for each analysis and depends on the signal-to-background ratio and on the transverse momentum.Particles are identified in the TOF by comparing the measured time of flight to the expected one for a given particle species.The cut is expressed in units of the estimated resolution σ TOF .The TOF allows pions and kaons to be unambiguously identified up to momentum p ≈ 1.5 GeV/c and also removes contamination from electrons.The two mesons can be distinguished from (anti)protons up to p ≈ 2.5 GeV/c.For K * 0 and φ reconstruction three TPC PID selection criteria are used, depending on the momentum of the daughter particle.Both pions and kaons are selected using a cut of | Nσ TPC |< 2.0 for p(K ± , π ± ) > 0.4 GeV/c.Here, p(K ± , π ± ) denotes the momenta of pions and kaons.Similarly, for p(K ± , π ± ) < 0.3 GeV/c, a cut of |Nσ TPC | < 6.0 is applied, while a cut of |Nσ TPC | < 4.0 for 0.3 < p(K ± , π ± ) < 0.4 GeV/c is applied.For the new analysis of the K * 0 (φ ) at √ s = 7 TeV, the specific energy loss for pion and kaon candidates is required to be within 2 (3) σ TPC of the expected mean, irrespective of the momentum.Also, a TOF 3σ TOF veto cut is applied for K * 0 for both √ s = 7 and 8 TeV."TOF veto" means that the TOF 3σ cut is applied only for cases where the track matches a hit in the TOF.

Raw yield extraction
The K * 0 (φ ) meson is reconstructed through its dominant hadronic decay channel K * 0 → π ± K ∓ (φ → K + K − ) by calculating the invariant mass of its daughters at the primary vertex.The invariant mass distribution of the decay daughter pairs is constructed taking unlike-sign pairs of K and π (K) candidates for K * 0 (φ ) in the same event.The rapidity of the πK (KK) pairs is required to lie within the range |y pair | < 0.5.As an example, the πK (KK) invariant mass distribution for √ s = 8 TeV is shown in Fig. 1 for 0 < p T < 0.2 GeV/c (0.6 < p T < 0.7 GeV/c).The shape of the uncorrelated background is obtained via the event mixing technique, calculating the invariant mass distribution of unlike-sign π ± K ∓ (K * 0 ) or K + K − (φ ) combinations from different events, √ s = 8 TeV ALICE Collaboration as shown in upper panel of Fig. 1.To avoid mismatch due to different acceptances and to assure a similar event structure, only tracks from events with similar vertex positions (∆z < 1 cm) and track multiplicities (∆n < 5) were mixed.For the φ meson in pp collisions at √ s = 7 TeV, the multiplicity difference for event mixing is restricted to ∆n ≤ 10.To reduce statistical uncertainties each event was mixed with 5 other similar events.For √ s = 8 TeV, the mixed event background is normalized in the mass range 1.1 < M Kπ < 1.5 GeV/c 2 (1.04 < M KK < 1.06 GeV/c 2 ) for K * 0 (φ ) so that it has the same integral as the unlike-charge distribution in that normalization region.For √ s = 7 TeV, the mixed event background is normalized in the mass range 1.1 < M Kπ < 1.15 GeV/c 2 and 1.048 < M KK < 1.052 GeV/c 2 for K * 0 and φ , respectively.This combinatorial background is subtracted from the unlike-charge mass distribution in each p T bin.Due to an imperfect description of the combinatorial background, as well to the presence of a correlated background, a residual background still remains.The correlated background can arise from correlated Kπ (KK) pairs for K * 0 (φ ), misidentified particle decays or jets.
The K * 0 raw yield is extracted from the Kπ invariant mass distribution in different p T bins between 0 and 20 GeV/c.After the combinatorial background subtraction the invariant mass distribution is fitted with the combination of a Breit-Wigner function for the signal peak and a second-order polynomial for the residual background.The fit function for K * 0 is given by Here m 0 is the fitted mass pole of the K * 0 , Γ 0 is the resonance width and A is the yield of the K * 0 meson.B, C and D are the fit parameters in the second-order polynomial.
The φ raw yield is extracted from the KK invariant mass distribution in different p T bins between 0.4 and 16 GeV/c after the combinatorial background subtraction.For the φ fit function, the detector mass resolution is taken into account due to the smaller width of the φ meson.This is achieved by using a Breit-Wigner function convoluted with a Gaussian function, which is known as Voigtian function.The KK invariant mass distribution is fitted with the combination of a Voigtian function for the signal peak and a second-order polynomial for the residual background.The fit function for φ is given by Here m 0 is the fitted mass pole of the φ , Γ 0 is the resonance width fixed to the value in vacuum and σ is the p T -dependent mass resolution, which ranges from 1 to 3 MeV/c 2 .
To extract the raw yields of K * 0 (φ ), for each p T bin the invariant mass histogram is integrated over the region 0.801 < m K * 0 < 0.990 (1.01 < m φ < 1.03), i.e. a range of three times the nominal width around the nominal mass.The integral of the residual background function in the same range is then subtracted.
To also consider the contribution from the tails outside the integration regions, yields are extracted from the signal peak fit function and added to the yields calculated from the histogram.

Normalisation and correction
The K * 0 and φ raw yields (N raw ) are normalised to the number of inelastic pp collisions and corrected for the branching ratio (BR), vertex selection, detector geometric acceptance (A) and efficiency (ε) and signal loss.The K * 0 and φ corrected yields are obtained by Here ε rec = A × ε is the correction that accounts for the detector acceptance and efficiency.The ε SL is the signal loss correction factor and accounts for the loss of K * 0 (φ ) mesons incurred by selecting events that satisfy only the ALICE minimum bias trigger, rather than all inelastic events.This is a particle species and p T -dependent correction factor which is peaked at low p T , indicating that events that fail the trigger selection have softer p T spectra than the average inelastic event.The signal loss correction factor is about 1% at low-p T and negligible for p T > 1 GeV/c.This correction is the ratio of the p T spectrum from inelastic events to the p T spectrum from triggered events and it is evaluated using Monte Carlo simulations.
N evt is the number of triggered events and a trigger efficiency (f norm ) is used to normalize the yield to the number of inelastic pp collisions.The value of the inelastic normalization factor for pp collisions at √ s = 8 TeV is 0.77 ± 0.02, which is the ratio between the V0 visible cross section [17] and the inelastic cross section [18].Similarly, we correct the yield with f vtx , which is the ratio of the number of events for which a good vertex was found to the total number of triggered events.This is estimated to be 0.972.The new results at 7 TeV are normalized as in [12].
The A × ε correction factor is determined with a Monte Carlo simulation using PYTHIA8 as event generator and GEANT3 [19] as transport code for the simulation of the detector response.The A × ε is obtained as the fraction of K * 0 and φ reconstructed after passing the same event selection and track quality cuts as used for the real event to the total number of generated resonances.This A × ε value is small at low p T and increases with increasing p T .This value is independent of p T above 5-6 GeV/c [12].

Systematic uncertainties
The systematic uncertainties on p T -differential yield, summarised in Table 1, are due to different sources such as signal extraction, background subtraction, track selection, global tracking uncertainty, knowledge of the material budget and the hadronic interaction cross section.
The systematic uncertainties associated to the signal extraction are estimated by varying the fitting ranges, the order of residual backgrounds (from 1 st order to 3 rd order), the width parameter and the mixed event background normalization range.The signal extraction systematic uncertainties also include the background subtraction systematic uncertainties, which are estimated by changing the methods used to estimate the combinatorial background (like-sign and event-mixing).The PID cuts and the track quality selection criteria are varied to obtain the systematic uncertainties due to the track selection.The relative uncertainties due to signal extraction and track selection for K * 0 (φ ) are 8.7% (1.9%) and 4% (2%), respectively at The global tracking uncertainty is calculated using ITS and TPC clusters for charged decay daughters.
The relative systematic uncertainty due to the global tracking efficiency is 3% for charged particles, which results in a 6% effect for the πK and KK pairs used in the reconstruction of the K * 0 and φ , respectively.The systematic uncertainty due to the residual uncertainty in the description of the material in the Monte Carlo simulation contributes up to 3.4% for K * 0 (3.1% for φ ).The systematic uncertainty due to the hadronic interaction cross section in the detector material is estimated to be up to 2.8% for K * 0 and up to 5.4% for φ .The uncertainties are accordingly propagated to the K * 0 and φ [20,21].The total systematic uncertainties, which are found to be p T dependent, range in from 11.3% to 12.1% for K * 0 and from 6.7% to 9.1% for φ .The uncertainties at √ s = 7 TeV are similarly estimated, totalling to comparable values, as seen in Table 1.To keep consistency with the published results, the systematic uncertainty due to the hadronic interaction cross section in the detector material and material budget uncertainties for √ s = 7 TeV are considered negligible [12].
4 Results and discussion

Transverse momentum spectra and differential yield ratios
Here, we report the measurement of K * 0 and φ in inelastic pp collisions at √ s = 8 TeV in the range up to p T = 20 GeV/c for K * 0 and up to p T = 16 GeV/c for φ .Also, we present the new measurements of K * 0 and φ in inelastic pp collisions at √ s = 7 TeV in the range up to p T = 20 GeV/c for K * 0 and up to p T = 21 GeV/c for φ .For both energies, the first bin of K * 0 starts at p T = 0 GeV/c and for φ , it starts at p T = 0.4 GeV/c.In Fig. 2, we show the transverse momentum spectra of K * 0 and φ at midrapidity |y| < 0.5 and fitted with the Lévy-,Tsallis distribution [22,23].The ratio of data to Lévy-Tsallis fit shows good agreement of data with model within systematic uncertainties.The fit parameters are shown in Table 2.The energy evolution of the transverse momentum spectra for K * 0 and φ is studied by calculating the ratio of p T -differential yields for inelastic events at √ s = 7 and 8 TeV to that at √ s = 2.76 TeV [24].This is shown in Fig. 3.The differential yield ratio to 2.76 TeV is consistent for 7 and 8 TeV within systematic uncertainties.The systematic uncertainties at both collision energies are largely uncorrelated.Therefore, the quadratic sum of those is taken as systematic uncertainties on the ratios.For both K * 0 and φ , the differential yield ratio is independent of p T within systematic uncertainties up to about 1 GeV/c for the different collision energies.This suggests that the particle production mechanism in soft scattering regions is independent of collision energy over the measured energy range.An increase in slope of differential yield ratios is observed for p T > 1-2 GeV/c.

p T -integrated yields
Table 3 shows the K * 0 and φ integrated yield (dN/dy) and mean transverse momenta ( p T ) in inelastic pp collisions at √ s = 8 TeV.As the φ spectrum starts from 0.4 GeV/c, for the calculation of dN/dy and p T , the spectrum is extrapolated down to p T = 0 GeV/c using a Lévy -Tsallis fit [22,23].The extrapolated part amounts to about 15% of the yield.Alternative fit functions (Boltzmann distribution, Bose-Einstein distribution, power-law, m T exponential and p T exponential) have been tried for the extrapolation, giving a contribution of 1.5% to the total systematic uncertainty on dN/dy.In case of K * 0 , no extrapolation is needed as the distribution is measured for p T > 0 GeV/c.Table 3 also shows the dN/dy and p T of φ at √ s = 7 TeV.The dN/dy and p T of the re-analysed K * 0 remains unchanged as reported in [12].
Table 3: K * 0 and φ integrated yields and p T in inelastic pp collisions at √ s = 7 and 8 TeV.The systematic uncertainties include the contributions from the uncertainties listed in Table 1 and the choice of the spectrum fit function for extrapolation is also included for the φ .Here, "stat."and "sys."refer to statistical and systematic uncertainties, respectively.

Particle ratios
For the calculation of the particle ratios, the values of dN/dy for π + + π − and K + +K − in pp collisions at √ s = 8 TeV are estimated via extrapolation using the data points available at different LHC collision energies [10,11] namely 0.9 and 7 TeV.The data points are fitted with the following polynomial function, Here A, n and B are the fit parameters.For the calculation of the uncertainties on the extrapolated value, the central values of the data points are shifted within their uncertainties and fitted with the same function.The π + + π − and K + +K − energy extrapolated yields in inelastic pp collisions at √ s = 8 TeV are 4.80 ± 0.21 and 0.614 ± 0.032.Here onwards, π + + π − is denoted as π and K + +K − is denoted as K.
Figure 4 shows the ratio of the dN/dy of K * 0 (φ ) to that of π in the left (right) panel, as a function of the collision energy.π has no strangeness content, K * 0 has one unit of strangeness, and φ is strangeness neutral but contains two valence strange (anti)quarks.It is observed that the K * 0 /π and φ /π ratios are independent of the collision energy within systematic uncertainties, which indicates that the chemistry of the system is independent of the energy from the RHIC to LHC energies.This also suggests that the strangeness production mechanisms do not depend on energy in inelastic pp collisions at LHC energies.Figure 4 and Ref. [12] show that this flat behaviour is observed from RHIC to LHC energies and the new result at √ s = 8 TeV is in agreement with previous findings.It is worth stressing that this flat behaviour is not trivial: since particle yields do in fact increase with the collision energy, the flat ratios are indicative of the fact that the percentage increase of dN/dy for π, K * 0 and φ as a function of the collision energy are similar from RHIC to LHC.
It is interesting to compare the particle ratios, K * 0 /K and φ /K measured in inelastic pp collisions with different collision systems and collision energies in order to understand the production dynamics.In the left and right panel of Fig. 5 the ratio K * 0 /K and φ /K is plotted as a function of center-of-mass energy per nucleon pairs for different collision systems.The K * 0 /K and φ /K ratios are independent of the collision energy and of the colliding system.The only exception is the K * 0 in central nucleus-nucleus collisions; we attribute the suppression of the K * 0 /K ratio to final state effects in the late hadronic stage [25].The behaviours of these ratios in pp collisions agree with the predictions [25,26] of a thermal model in the grand-canonical limit.
The ratio φ /K * 0 ratio as a function of center-of-mass energy is plotted in Fig. 6.The ratio seems to be independent of collision energy and appears to follow a behavior expected from thermal production, within experimental uncertainties.√ s = 8 TeV ALICE Collaboration   [10-12, 27-30, 32-41] as a function of the collision energy.Bars (when present) represent statistical uncertainties.Boxes represent the total systematic uncertainties or the total uncertainties for cases when separate statistical uncertainties were not reported.The value given by a grand-canonical thermal model with a chemical freeze-out temperature of 156 MeV [26] is also shown.

Comparison to models
QCD-inspired MC event generators like PYTHIA 8 [7], PHOJET [8,9] and EPOS-LHC [6] are used to study multi-particle production, which is predominantly a soft, non-perturbative process.The measurements are compared with the MC model predictions.PYTHIA 8 and PHOJET use the Lund string fragmentation model [42] for the hadronisation of light and heavy quarks.We compare our data with the Monash 2013 tune [7] for PYTHIA 8, which is an updated parameter set for the Lund hadronisation compared to previous tunes.To describe the non-perturbative phenomena (soft/semi-hard processes), PY-THIA 8 includes multiple parton−parton interactions while PHOJET uses the Dual Parton Model [43].For hard scatterings, particle production in both models is based on perturbative QCD and only consider two particle scatterings.For multiple scatterings, the EPOS-LHC model invokes Gribov's Reggeon Field Theory [44], which features a collective hadronisation via the core-corona mechanism [45].The final √ s = 8 TeV ALICE Collaboration  [12,25,27,28] as a function of the collision energy.Bars (when present) represent statistical uncertainties.Boxes represent the total systematic uncertainties or the total uncertainties for cases when separate statistical uncertainties were not reported.
state partonic system consists of longitudinal flux tubes which fragment into string segments.The high energy density string segments form the so-called "core" region, which evolves hydrodynamically to form the bulk part of the system in the final state.The low-density region is known as the "corona", which expands and breaks via the production of quark-antiquark pairs and hadronises using the vacuum string fragmentation.Recent data from LHC have been used already to tune the EPOS-LHC model [6].
Figure 7 shows a comparison of the K * 0 (left) and φ (right) p T spectra in inelastic pp collisions with PYTHIA8, PHOJET and EPOS-LHC.The bottom panels show the ratios of the p T spectra from models to the measured p T spectra by ALICE.The total fractional uncertainties from the real data, including both statistical and systematic uncertainties are shown as shaded boxes.PYTHIA 8 overestimates the p T spectra for K * 0 at very low p T but describes in the intermediate-p T region, which approaches the experimental data at high p T .For the φ meson, PYTHIA 8 under predicts the yields from the experimental data by about a factor of two.PHOJET has a softer p T spectrum for K * 0 and it explains the data above p T > 4 GeV/c.For the φ meson, PHOJET predicts the yields similarly as PHYTHIA 8 at low p T , while it approaches the experimental data at higher p T .For the K * 0 , EPOS-LHC describes the p T spectra at low p T and overestimates the data above 4 GeV/c.For the φ meson when PYTHIA and PHOJET fail to describe the p T -spectra, the EPOS-LHC model approaches to the data at low p T and deviates monotonically from it with increasing p T .

Conclusions
The measurements are presented for K * 0 and φ production at midrapidity in inelastic pp collisions at √ s = 8 TeV in the range 0 < p T < 20 GeV/c for K * 0 and 0.4 < p T < 16 GeV/c for φ .Also, updated measurements at √ s = 7 TeV are presented, which improve the results previously published in [12].In comparison to other LHC energies, a hardening of the p T spectra is observed with an increasing collision energy.The K * 0 /π and φ /π ratios are independent of collision energy within systematic uncertainties.This indicates that there is no strangeness enhancement in inelastic pp collisions as the collision energy is increased.Similar behavior is observed for the K * 0 /K and φ /K ratios as a function of collision energy.Also, no energy dependence of the φ /K * 0 ratio in minimum bias pp collisions at LHC energies is observed, which suggests there is no energy dependence of the chemistry of the system.None of the MC models seem to explain the K * 0 spectra in complete p T region whereas PHOJET and PYTHIA describe the data for intermediate and high-p T regions.However, the MC models fail to explain the p T spectra of   [7], PHOJET [8,9] and EPOS-LHC ??.The bottom plots show the ratios of the p T spectra from the models to the measured p T spectra by ALICE.The total fractional uncertainties from data are shown as shaded boxes.φ meson completely.These pp results will serve as baseline for the measurements in p-Pb and Pb-Pb collisions.
The ALICE Collaboration would like to thank all its engineers and technicians for their invaluable contributions to the construction of the experiment and the CERN accelerator teams for the outstanding performance of the LHC complex.

Figure 1 :
Figure 1: (Color online) (Upper panels) Invariant mass distributions (closed black point) for the K * 0 (left) and φ (right) in pp collisions at 8 TeV in the p T range 0 < p T < 0.2 GeV/c and 0.6 < p T < 0.7 GeV/c, respectively.The combinatorial background (open red circles) is estimated using unlike-sign pairs from different events (mixed event).The statistical uncertainties are shown as bars.(Lower panels) Kπ (left) and KK (right) invariant mass distributions in the same p T ranges after combinatorial background subtraction together with the fits to the signal and background contribution.

Figure 2 :
Figure 2: (Color online) Upper panel shows the p T spectra of K * 0 and φ in inelastic pp collisions at 7 TeV (left) and 8 TeV (right) and fitted with the Lévy-Tsallis distribution [22, 23].The normalisation uncertainty in the spectra is +7.3 −3.5 % for 7 TeV and 2.69% for 8 TeV.The vertical bars show statistical and the boxes show systematic uncertainties.The lower panels show the ratio of data to the Lévy-Tsallis fit.Here, the bars show the systematic uncertainty.

Figure 3 :
Figure 3: (Color online) Ratios of transverse-momentum spectra of K * 0 and φ in inelastic events at √ s = 7 and 8 TeV to the transverse-momentum spectra in pp collisions at √ s = 2.76 TeV.The statistical and systematic uncertainties are shown as vertical error bars and boxes, respectively.The normalisation uncertainties are indicated by boxes around unity.

Figure 4 :
Figure4: (Color online) Particle ratios of K * 0 /π (left) and φ /π (right) are presented for pp collisions as a function of the collision energy.Bars (when present) represent statistical uncertainties.Boxes represent the total systematic uncertainties or the total uncertainties for cases when separate statistical uncertainties were not reported.[10-12,25, 27-32]

Figure 5 :
Figure 5: (Color online) Particle ratios of K * 0 /K (left) and φ /K (right) are presented for pp, highmultiplicity p-Pb, central d-Au, and central A-A collisions[10-12, 27-30, 32-41]  as a function of the collision energy.Bars (when present) represent statistical uncertainties.Boxes represent the total systematic uncertainties or the total uncertainties for cases when separate statistical uncertainties were not reported.The value given by a grand-canonical thermal model with a chemical freeze-out temperature of 156 MeV[26] is also shown.

Figure 6 :
Figure 6: (Color online) Particle ratio φ / K * 0 presented for pp collisions[12,25,27,28] as a function of the collision energy.Bars (when present) represent statistical uncertainties.Boxes represent the total systematic uncertainties or the total uncertainties for cases when separate statistical uncertainties were not reported.

Figure 7 :
Figure7: (Color online) Comparison of the K * 0 (left) and φ (right) p T spectra measured in inelastic pp collisions with those obtained from PYTHIA8 (Monash tune)[7], PHOJET[8,9] and EPOS-LHC ??.The bottom plots show the ratios of the p T spectra from the models to the measured p T spectra by ALICE.The total fractional uncertainties from data are shown as shaded boxes.
The ALICE Collaboration gratefully acknowledges the resources and support provided by all Grid centres and the Worldwide LHC Computing Grid (WLCG) collaboration.The ALICE Collaboration acknowledges the following funding agencies for their support in building and running the ALICE detector: A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences, Austrian Science Fund (FWF): [M 2467-N36] and Nationalstiftung für Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Universidade Federal do Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep) and Fundac ¸ão de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil; Ministry of Science & Technology of China (MSTC), National Natural Science Foundation of China (NSFC) and Ministry of Education of China (MOEC) , China; Croatian Science Foundation and Ministry of Science and Education, Croatia; Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba; Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research -Natural Sciences, the Carlsberg Foundation and Danish National Research Foundation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat à l'Energie Atomique (CEA), Institut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS) and Région des Pays de la Loire, France; Bundesministerium für Bildung und Forschung (BMBF) and GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany; General Secretariat for Research and Technology, Ministry of Education, Research and Religions, Greece; National Research, Development and Innovation Office, Hungary; Department of Atomic Energy Government of India (DAE), Department of Science and Tech-

Table 1 :
Systematic uncertainties in the measurement of K * 0 and φ yields in pp collisions at √ s = 7 and 8 TeV.The global tracking uncertainty is p T -independent, while the other single-valued systematic uncertainties are averaged over p T .The values given in ranges are minimum and maximum uncertainties depending on p T .

Table 2 :
Parameters extracted from the Lévy-Tsallis fit to the K * 0 and φ transverse momentum spectra in inelastic pp collisions at √ s = 7 and 8 TeV.